Thermo-Economic Analysis of Innovative Integrated Power Cycles for Low-Temperature Heat Sources Based on Heat Transformer

Abstract

This paper proposes two novel integrated power cycles as appropriate systems for low-temperature heat sources. The proposed cycles encompass an absorption heat transformer (AHT) system to convert low-temperature heat source to high-temperature source and supply the required heat for driving Kalina cycle (KC) and absorption power cycle (APC) as bottoming cycles. A comprehensive simulation of the system is presented based on the thermo-economic viewpoint. The results show that the AHT/KC has higher energy and exergy efficiencies than the AHT/APC, with 7.69% and 49.03%, respectively. In addition, the sum unit cost of the product (SUCP) for the system is calculated 87.72 $/GJ. According to the results, throttle valve 1 and absorber 1 are the most destructive components of the AHT/KC and AHT/APC, respectively. The net output power in the AHT/KC and the AHT/APC is assessed 60.06 kW and 34.86 kW, respectively. The circulation rate (CR), Coefficient of performance (COP), and exergetic coefficient of performance (ECOP) for both cycles are 3.819, 0.4108, and 0.6107, respectively. The study of key parameters demonstrates that the energetic performance of the proposed power cycles increases and decreases by a rise in the temperature of the generator and condenser, respectively. From the exergetic perspective, rising temperature of the generator improves the efficiency of the cycles, while increasing the ammonia concentration as well as condenser and absorber temperatures reduce the exergy efficiency.

1. Introduction

The continuous growth of the population has increased the demand for sustainable energy supply throughout the world. A large part of the required energy is supplied through the consumption of fossil fuels, which are the main cause of environmental pollution and global warming [1]. This desperate situation has led the concentration of researchers towards other energy resources to study their merits and potential for addressing energy demands [2]. In this regard, improving the efficiency of the energy conversion systems can be imperative for the reduction of their adverse impacts on the environment. In addition, a colossal amount of energy can be obtained through low-temperature resources such as recovering industrial waste heat and harnessing natural energy. Despite restrictions in the direct use of these resources in a majority of industrial processes due to their low-temperature characteristics, they can be recovered by employing appropriate energy converters to increase their temperature. Several approaches have been taken into account to address this matter, among which using heat pump systems (HPs) is one of the best. HPs are generally classified into three types of absorption heat transformers (AHT) [3], absorption-compression heat pumps (ACHP) [4], and vapor compression heat pumps (VCHP) [5]. The main disadvantage of VCHP and ACHP systems is that they need an immense amount of electricity. The AHT system, however, requires a subtle amount of electricity since it is driven by waste heat. Meantime, the performance of VCHP systems can be improved by using proper types of organic refrigerants to compete with ACHP systems. Nevertheless, using organic refrigerants in VCHP systems can degrade the operation class of the whole unit [6]. All in all, it can be claimed that waste thermal heat can drive an ammonia-water mixture heat pump system such as an AHT unit better than electricity based on converting a low-temperature heat source to a relatively high or medium temperature source.

An AHT is responsible for transferring heat from a low-temperature level to a high-temperature level through an absorption process. A detailed investigation on AHTs by Huicochea et al. [7] shows a reduction in values of coefficient of performance (COP) and exergetic coefficient of performance (ECOP) by enhancement of the absorber temperature. In addition, over 50% of the system irreversibility belongs to the absorber. In research by Liu et al. [8], the maximum of ECOP and COP of a 100 kW vapor generation system combined with a solar-based AHT was calculated 0.802 and 0.502, respectively. Singh et al. [9] investigated exergy destruction minimization and component-wise variation in exergy destruction for an Ammonia-Water Absorption Refrigeration System. Yari et al. [10] presented a cogeneration cycle to produce power and fresh water retrieving the waste heat of an ejector-expansion trans-critical CO₂ refrigeration cycle. In the proposed system, they utilized an AHT to raise the temperature of waste heat to run a desalination system. Jain and Sachdeva [11] implemented energy, exergy, and economic (3E) analyses on AHT working with LiBr-H₂O fluid and evaluated the effect of operating variables on the size, system performance, and cost. The results of the thermodynamic and thermoeconomic performance of the system indicated higher irreversibility for heat exchangers with a lower investment cost. Thus, the influence of variables of systems was determined economically and thermodynamically by employing the non-dominated sort of genetic algorithm-II (NSGA-II) technique. Sun et al. [12] conducted the thermodynamic analysis of a new medium-low temperature hydrothermal geothermal district heating system based on heat pumps and an AHT. The results revealed that the centralized AHT can improve the performance of HPs and reduce irreversible loss of the heating station. Ghiasirad et al. [13] carried out the thermoeconomic analysis of a novel multi-generation system for heating, cooling, power, and desalination. They found that energy and exergy efficiencies are 70.58% and 43.59%, respectively, for winter, and 60.55% and 17.05%, respectively, for summer.

Zeotropic-based power plants have been introduced as an interesting alternative to conventional steam and organic Rankine cycles (SRC and ORC). Generally speaking, SRCs have lower efficiency in comparison with ORCs. Regarding this, recent studies have focused extensively on various innovative methods to promote the performance of ORCs. It is crucial to take into consideration the safety aspects of the ORC before installation [14]. However, ammonia-water mixture power plants such as absorption power cycles (APCs) and Kalina cycles (KCs) are recommended instead of ORCs to decrease the risk of explosion and fire caused by the use of flammable materials [15]. A study by Alexander Kalina [16] substantiated that the advantages of APCs outweigh those of the conventional Rankine cycles. Meantime, a KC is a promising thermodynamic cycle for power generation to recover the heat of low-temperature heat sources. The working fluid in KC is a mixture of at least two different fluids (usually NH₃ and H₂O). Some studies have demonstrated that KC can have better thermal efficiency than ORC [17]. For instance, in one of the recent studies carried out by Rostamzadeh et al. [18], it was found that using KC as a topping cycle for devising a micro-CCHP (combined cooling, heating, and power) cycle can be more efficient than using ORC. In other words, KCs can be efficiently driven by different heat sources, namely biomass fuel [19], geothermal heat source [20], solar energy [21], the waste heat of city gate stations [22], the waste heat of proton exchange membrane (PEM) fuel cell [23], cement kiln [24], and coal-fired steam power plant [25]. Wang et al. [19] optimized a biomass-fired KC and showed that the cycle with a regenerative heater is more efficient than the cycle without a regenerative heater. Ghaebi et al. [20] studied a system encompassing an ejector refrigeration cycle (ERC) and a KC for simultaneous power production and refrigeration. Considering both thermal and exergy efficiencies as objective functions, they performed single and multi-objective optimizations by employing the genetic algorithm (GA). In this case, the optimum thermal efficiency, exergy efficiency, net output power, and refrigeration, were calculated 15%, 47.8%, 2319 kW, and 1133 kW, respectively. Moreover, among all components, condenser 1 accounted for the most exergy destruction rate followed by vapor generator. A novel combined power and ejector refrigeration cycle was investigated by Ghaebi et al. [26]. The exhaust of the turbine was used as the primary flow of the ejector to draw the secondary flow into the ejector. Based on the selected objective functions, they achieved the optimal performance of the cycle when evaporator temperature, heat source temperature, condenser pinch point temperature, vapor generator pressure, ammonia concentration, and expander ratio were 285 K, 473 K, 8 K, 17.5 bar, 15%, and 2.5, respectively. In the optimal condition, the thermal and exergy efficiencies and SUCP of the system were 20.4%, 16.69%, and 2466.36 $/MWh, respectively. Cao et al. [27] recommended a combined cycle, consisting of a KC and an absorption cooling cycle (ACC) driven by a low-temperature heat source. Based on the exergy optimization, it was found that increasing the inlet pressure of the expander and concentration of NH₃-H₂O basic solution improves the exergy efficiency. In addition, variation in high-temperature, low-temperature recuperators and terminal temperature difference does not affect the refrigeration exergy. Mahmoudi et al. [28] used the advanced exergy technique in a KC driven by a low-temperature geothermal source. The results represented that in all components of the system (except evaporator), the highest rate of exergy destruction is related to the endogenous part. A novel parallel dual-pressure KC system for low-temperature geothermal energy was investigated by Zheng et al. [29]. The results represented that the proposed KC exhibits more excellent performance in terms of net power output and exergy efficiency than basic KC. Singh et al. [30] studied a new combined power and cooling cycle (CPCC) formed by the integration of modified Kalina and Goswami cycles sharing an absorber. This work clarified that the proposed improved exergy optimization procedure not only minimized the exergy destruction of the overall cycle, but it also ensured the optimum attainment of total turbine work output, cooling output and exergy efficiency of the cycle.

In a recent study, a novel cooling and power cogeneration cycle based on APC and booster-assisted refrigeration cycle was tested by Wang et al. [31]. The booster was embedded between the ejector and evaporator to increase the cooling production. The proposed combined cycle was operated by utilizing the thermal energy of a low-temperature heat source. The results proved that the energy efficiency of the booster-assisted cycle is greater than that of the conventional APC. Ayou et al. [32] investigated the operational flexibility and performance improvement of a single-stage hybrid absorption power and refrigeration cycle combined with a compression booster. The booster was employed between the evaporator and absorber. Energy, exergy, and exergoeconomic analysis of a novel combined cooling and power (CCP) system based on the APC and geothermal energy as a low-temperature heat source was presented by Parikhani et al. [33]. A thermodynamic analysis of the modeled CCP system was conducted to determine the performance characteristics and main origin of irreversibility of the system for a better thermal design purpose. It was found that the modeled system can produce 221.4 kW cooling and 161.2 kW net output power out of 2333 kW heat gained from the geothermal source. The overall SUCP, thermal efficiency, and exergy efficiency of the system were 93.87 $/GJ, 16.4%, and 28.95%, respectively.

Based on the above-discussed literature, it is figured out that due to the pervasive characteristics of low-temperature heat sources (industrial waste heat, geothermal resource, etc.), converting these low valuable sources to high-temperature sources with affordable electrical power consumption from the network can be a demanding technology. The generated high-temperature heat sources can later be used for more valuable products. In this study, the high-temperature heat is converted into electricity by employing two different ammonia-water systems, namely KC and APC. The AHT system is used as a topping cycle, and KC and APC are used as bottoming cycles. Based on the present investigation, the ammonia-water mixture power system is evaluated from the first and second laws of thermodynamics as well as economic vantage points. A comprehensive simulation of the devised enhanced power cycle is presented to recommend several procedures to improve the energetic and exergetic performance of the proposed set-up while decreasing the electricity cost of the unit.

2. System Statement

Figure 1 outlines the sketch of the recommended systems, namely integrated AHT/KC and AHT/APC systems. The basic components of the AHT are an evaporator, a generator, an absorber, a condenser, a solution heat exchanger (SHX), a throttling valve, and two pumps. The waste heat is given to the evaporator and generator. The waste heat in the generator separates the blend solution through a partially evaporating refrigerant. The rich solution is pre-heated by the return lean solution and is pumped to the absorber afterward. The condenser is used to liquefy the desorbed refrigerant vapor (state 1) from the generator. The liquefied vapor is pumped into the evaporator, and the vaporized refrigerant is generated in the evaporator at higher pressure by supplying waste heat to this element. Next, it heads towards the absorber, and consequently, the heat produced in the absorber increases [34]. The produced heat is then used to generate power via employing a KC (Figure 1a) and an APC (Figure 1b).

According to Figure 1a, the heat in the absorber is given to KC for power generation. The role of the separator in KC is separating the basic mixed solution into lean and rich solutions. The rich solution (state 12) moves towards the turbine to generate electricity via an expansion process, while the lean solution (state 13) goes to the regenerator to partially heat the pressurized liquid basic solution before entering the absorber. Next, it passes through a throttling valve (state 14) to be mixed with the output stream of the turbine in a mixer (state 16). The mixed fluid then passes through a condenser and then transfers its heat to the environment while condensing to saturated liquid (state 18). The liquid is pumped to the regenerator and then enters the absorber to complete the power generation cycle.

In the second part of this study, an APC is used instead of KC for power generation purposes (Figure 1b). According to Figure 1b, the needed heat for APC is supplied by absorber 1, which leads to the generation of lean and rich solutions at states 16 and 15, respectively. Meantime, ammonia flows to the turbine and generates electricity through an expansion process. The lean solution (state 16) goes to heat exchanger 2 and then is expanded via a throttling valve (state 18). The lean solution and ammonia are mixed in absorber 2 and are condensed to liquid with rich concentration. The rich solution leaves absorber 2 (state 13) and is pumped to heat exchanger 2. The temperature of the rich solution increases through the heat exchanger 2, and then it streams to absorber 1 and completes the cycle.

3. Mathematical Modeling

In this section of the paper, the devised set-ups are analyzed from thermodynamic and thermo-economic viewpoints. For this aim, an appropriate computer code is developed in the EES (Engineering Equation Solver) software based on the subsequent assumptions [35,36]:

• The systems work under steady conditions.
• The heat loss in the components and pressure drops in the pipelines are negligible.
• Variations in the potential and kinematic energies are not regarded.
• All turbines and pumps undergo an isentropic process.
• Outlets of condensers, evaporators, generators, and absorbers are presumed saturated.

Other than the above-mentioned presumptions, some required input data in the modeling process are given in

Table 1. Central input data for simulation of the devised enhanced power generation set-ups.

Parameter	Value
$\mathrm{Reference}\mathrm{temperature},T_0$ (K)	298
$\mathrm{Reference}\mathrm{pressure},P_0$ (bar)	1.013
$\mathrm{Geothermal}\mathrm{inlet}\mathrm{temperature},T_{Geo}$ (K)	363
$\mathrm{Evaporator}\mathrm{inlet}\mathrm{temperature},T_{Eva}$ (K)	363
$\mathrm{Geothermal}\mathrm{water}\mathrm{mass}\mathrm{flow}\mathrm{rate},{\dot{m}}_{Geo}$ (kg s−1)	10
$\mathrm{Geothermal}\mathrm{pressure},P_{Geo}$ (bar)	2.5
$\mathrm{Generator}\mathrm{pinch}\mathrm{point}\mathrm{temperature}\mathrm{difference},\Delta T_{PP,Gen}$ (K)	5
$\mathrm{Absorber}\mathrm{outlet}\mathrm{temperature}\mathrm{of}\mathrm{AHT},T_{Abs/Abs1}$ (K)	403
$\mathrm{Condenser}\mathrm{outlet}\mathrm{temperature}\mathrm{of}\mathrm{AHT},T_{Cond1/Cond}$ (K)	298
$\mathrm{Absorber}\mathrm{terminal}\mathrm{temperature}\mathrm{difference}\mathrm{of}\mathrm{AHT},TT{D}_{Abs/Abs1}$(K)	10
$\mathrm{Absorber}\mathrm{pressure}\mathrm{of}\mathrm{KC},P_{Abs1}$ (bar)	15
$\mathrm{Absorber}1\mathrm{pressure}\mathrm{of}\mathrm{APC},P_{Abs1}$ (bar)	12
$\mathrm{Ammonia}\mathrm{concentration}\mathrm{at}\mathrm{separator}\mathrm{inlet},X_B$ (%)	40
$\mathrm{Ammonia}\mathrm{concentration}\mathrm{at}\mathrm{Absorber}2\mathrm{outlet},X_B$ (%)	40
$\mathrm{Temperature}\mathrm{difference}\mathrm{in}\mathrm{Regenerator},(T_{14}-$$T_{19}$) (K)	10
$\mathrm{Condenser}2\mathrm{outlet}\mathrm{temperature},T_{Cond2}$ (K)	303
$\mathrm{Absorber}2\mathrm{outlet}\mathrm{temperature},T_{Abs2}$ (K)	316
Pump’s isentropic efficiency, ηis,Pum (%)	85
Turbine’s isentropic efficiency, ηis,Tur (%)	90
$\mathrm{Heat}\mathrm{exchanger}\mathrm{effectiveness},{\epsilon }_{HE}$ (%)	80

.

3.1. Thermodynamic Analysis

Generally, the mass and energy conservation relations under steady-state circumstances for a system are written as [37]:

$$\sum {\dot{m}}_{in}-\sum {\dot{m}}_{out}=0$$

(1)

$$\sum {\left(\dot{m}X\right)}_{in}-\sum {\left(\dot{m}X\right)}_{out}=0$$

(2)

$$\sum {\left(\dot{m}h\right)}_{in}-\sum {\left(\dot{m}h\right)}_{out}+\sum {\dot{Q}}_{in}-\sum {\dot{Q}}_{out}+\dot{W}=0$$

(3)

where, $h$, $\dot{m}$, $X$, $\dot{Q}$, and $\dot{W}$ are specific enthalpy, mass flow rate, ammonia concentration in the solution, heat transfer rate, and power generation rate, respectively.

Circulation rate (CR) is calculated according to the circulation of working fluid in the cycle. CR is defined as the ratio of the mass flow rate of the solution coming from the absorber to the generator $\left({\dot{m}}_7\right)$ to the mass flow rate of the working fluid $\left({\dot{m}}_1\right)$. Thus, CR is expressed as [38]:

$$CR=\frac{{\dot{m}}_7}{{\dot{m}}_1}$$

(4)

COP for an AHT is defined as the heat transfer rate in the absorber per the total heat transfer rate of the generator and evaporator [38]:

$$COP=\frac{Q_{AB}}{Q_{GE}+Q_{EV}}$$

(5)

Entropy generation in a constant control volume is written as follows [37]:

$${\dot{S}}_g=\sum {\dot{m}}_o{s}_o-\sum {\dot{m}}_i{s}_i-\sum \frac{Q_k}{T_k}$$

(6)

In Equation (6), ${\dot{S}}_g$, $s$, and $T$ indicate entropy generation rate, specific entropy, and temperature, respectively.

Exergy is the maximum theoretical useful work, which is achievable when the system performs relative to the dead state. In a closed cycle, ignoring the effects of kinetic and potential exergies of all flows, the entire exergy of the kth flow is written in terms of the following relation [37]:

$$\dot{E}x=\dot{E}{x}_{ph}+\dot{E}{x}_{ch}$$

(7)

where, $\dot{E}{x}_{ph}$ is the physical exergy rate as:

$$\dot{E}{x}_{ph}=\sum \dot{m}\left(h-h_0-T_0\left(s-s_0\right)\right)$$

(8)

Herein, $0$ indicates the reference point. In addition, $\dot{E}{x}_{ch}$ is the chemical exergy rate articulated as [33]:

$$\dot{E}{x}_{ch}={\dot{n}}_i\left[\sum Y_{i}e{x}_i^{ch,0}+\overline{R}{T}_0\sum Y_i\ln Y_i\right]$$

(9)

where, ${\dot{n}}_i$, $e_i^{-ch,0}$, and $\overline{R}$ signify molar flow rate of each element, standard chemical exergy for the elements, and universal gas constant, respectively.

Accordingly, the exergy balance relation can be stated as:

$$\dot{E}{x}_F=\dot{E}{x}_P+\dot{E}{x}_D+\dot{E}{x}_L$$

(10)

where, $\dot{E}{x}_F$, $\dot{E}{x}_P$, $\dot{E}{x}_D$, and $\dot{E}{x}_L$ are fuel exergy rate, product exergy rate, exergy destruction rate, and exergy loss rate, respectively. Moreover, the exergetic efficiency $\left({\eta }_{ex}\right)$ of a system is written as the following relation [37]:

$${\eta }_{ex}=\frac{\dot{E}{x}_P}{\dot{E}{x}_F}$$

(11)

Based on the above-mentioned relations, the energy and exergy balance relations for various components of the studied system are given in

Table 2. Energetic and exergetic relations for the devised integrated AHT/KC and AHT/APC set-ups.

Component	Mass and Energy Balance Equations	Exergy Equations
		Fuel	Product
(a) AHT/KC
Condenser1	${\dot{Q}}_{Cond1}={\dot{m}}_1\left(h_1-h_2\right)$, ${\dot{Q}}_{Cond1}={\dot{m}}_{25}\left(h_{26}-h_{25}\right)$, ${\dot{m}}_1={\dot{m}}_2$, ${\dot{m}}_{25}={\dot{m}}_{26}$	${\dot{Ex}}_1-{\dot{Ex}}_2$	${\dot{Ex}}_{26}-{\dot{Ex}}_{25}$
Generator	${\dot{Q}}_{Gen}={\dot{m}}_1{h}_1+{\dot{m}}_8{h}_8-{\dot{m}}_7{h}_7$, ${\dot{Q}}_{Gen}={\dot{m}}_{27}\left(h_{27}-h_{28}\right)$, ${\dot{m}}_7={\dot{m}}_1+{\dot{m}}_8$, ${\dot{m}}_7{X}_7={\dot{m}}_1{X}_1+{\dot{m}}_8{X}_8$, ${\dot{m}}_{27}={\dot{m}}_{28}$	${\dot{Ex}}_{27}-{\dot{Ex}}_{28}$	${\dot{Ex}}_1+{\dot{Ex}}_8-{\dot{Ex}}_7$
Pump2	${\dot{W}}_{Pum2}={\dot{m}}_2\left(h_3-h_2\right)$, ${\eta }_{is,Pum2}=\frac{h_{3s}-h_2}{h_3-h_2}$, ${\dot{m}}_2={\dot{m}}_3$	${\dot{W}}_{Pum2}$	${\dot{Ex}}_3-{\dot{Ex}}_2$
Pump1	${\dot{W}}_{Pum1}={\dot{m}}_8\left(h_9-h_8\right)$, ${\eta }_{is,Pum2}=\frac{h_{9s}-h_8}{h_9-h_8}$, ${\dot{m}}_8={\dot{m}}_9$	${\dot{W}}_{Pum1}$	${\dot{Ex}}_9-{\dot{Ex}}_8$
T.V1	$h_6=h_7$, ${\dot{m}}_6={\dot{m}}_7$	${\dot{Ex}}_6$	${\dot{Ex}}_7$
Heat Exchanger	${\dot{Q}}_{HE}={\dot{m}}_5\left(h_5-h_6\right)$, ${\epsilon }_{HE}=\frac{h_{10}-h_9}{h_5-h_9}$, ${\dot{m}}_5={\dot{m}}_6$, ${\dot{m}}_9={\dot{m}}_{10}$	${\dot{Ex}}_5-{\dot{Ex}}_6$	${\dot{Ex}}_{10}-{\dot{Ex}}_9$
Evaporator	${\dot{Q}}_{Eva}={\dot{m}}_4\left(h_4-h_3\right)$, ${\dot{Q}}_{Eva}={\dot{m}}_{23}\left(h_{23}-h_{24}\right)$, ${\dot{m}}_3={\dot{m}}_4$, ${\dot{m}}_{23}={\dot{m}}_{24}$	${\dot{Ex}}_{23}-{\dot{Ex}}_{24}$	${\dot{Ex}}_4-{\dot{Ex}}_3$
Absorber	${\dot{Q}}_{Abs}={\dot{m}}_4{h}_4+{\dot{m}}_{10}{h}_{10}-{\dot{m}}_5{h}_5$, ${\dot{Q}}_{Abs}={\dot{m}}_{11}{h}_{11}-{\dot{m}}_{20}{h}_{20}$ ${\dot{m}}_5={\dot{m}}_4+{\dot{m}}_{10}$, ${\dot{m}}_{11}={\dot{m}}_{20}$	${\dot{Ex}}_4+{\dot{Ex}}_{10}-{\dot{Ex}}_5$	${\dot{Ex}}_{11}-{\dot{Ex}}_{20}$
Separator	${\dot{m}}_{11}{h}_{11}={\dot{m}}_{12}{h}_{12}+{\dot{m}}_{13}{h}_{13}$, ${\dot{m}}_{11}={\dot{m}}_{12}+{\dot{m}}_{13}$	${\dot{Ex}}_{11}$	${\dot{Ex}}_{12}+{\dot{Ex}}_{13}$
Turbine	${\dot{W}}_{Tur}={\dot{m}}_{12}\left(h_{12}-h_{16}\right)$, ${\eta }_{is,Pum2}=\frac{h_{12}-h_{16}}{h_{12}-h_{16s}}$, ${\dot{m}}_{12}={\dot{m}}_{16}$	${\dot{Ex}}_{12}-{\dot{Ex}}_{16}$	${\dot{W}}_{Tur}$
Regenerator	${\dot{Q}}_{Reg}={\dot{m}}_{13}\left(h_{13}-h_{14}\right)$, ${\dot{Q}}_{Reg}={\dot{m}}_{19}\left(h_{20}-h_{19}\right)$, ${\dot{m}}_{13}={\dot{m}}_{14}$, ${\dot{m}}_{19}={\dot{m}}_{20}$	${\dot{Ex}}_{13}-{\dot{Ex}}_{14}$	${\dot{Ex}}_{20}-{\dot{Ex}}_{19}$
T.V2	$h_{14}=h_{15}$, ${\dot{m}}_{14}={\dot{m}}_{15}$	${\dot{Ex}}_{14}$	${\dot{Ex}}_{15}$
Mixer	${\dot{m}}_{17}{h}_{17}={\dot{m}}_{15}{h}_{15}+{\dot{m}}_{16}{h}_{16}$, ${\dot{m}}_{17}={\dot{m}}_{15}+{\dot{m}}_{16}$	${\dot{Ex}}_{15}+{\dot{Ex}}_{16}$	${\dot{Ex}}_{17}$
Pump3	${\dot{W}}_{Pum3}={\dot{m}}_{18}\left(h_{19}-h_{18}\right)$, ${\eta }_{is,Pum3}=\frac{h_{19s}-h_{18}}{h_{19}-h_{18}}$, ${\dot{m}}_{18}={\dot{m}}_{19}$	${\dot{W}}_{Pum3}$	${\dot{Ex}}_{19}-{\dot{Ex}}_{18}$
Condenser2	${\dot{Q}}_{Cond}={\dot{m}}_1\left(h_1-h_2\right)$, ${\dot{Q}}_{Cond}={\dot{m}}_{25}\left(h_{26}-h_{25}\right)$, ${\dot{m}}_{17}={\dot{m}}_{18}$, ${\dot{m}}_{21}={\dot{m}}_{22}$	${\dot{Ex}}_{17}-{\dot{Ex}}_{18}$	${\dot{Ex}}_{22}-{\dot{Ex}}_{21}$
(b) AHT/APC
Condenser	${\dot{Q}}_{Cond}={\dot{m}}_1\left(h_1-h_2\right)$, ${\dot{Q}}_{Cond}={\dot{m}}_{25}\left(h_{26}-h_{25}\right)$, ${\dot{m}}_1={\dot{m}}_2$, ${\dot{m}}_{25}={\dot{m}}_{26}$	${\dot{Ex}}_1-{\dot{Ex}}_2$	${\dot{Ex}}_{26}-{\dot{Ex}}_{25}$
Generator	${\dot{Q}}_{Gen}={\dot{m}}_1{h}_1+{\dot{m}}_8{h}_8-{\dot{m}}_7{h}_7$, ${\dot{Q}}_{Gen}={\dot{m}}_{19}\left(h_{19}-h_{20}\right)$, ${\dot{m}}_7={\dot{m}}_1+{\dot{m}}_8$, ${\dot{m}}_7{X}_7={\dot{m}}_1{X}_1+{\dot{m}}_8{X}_8$, ${\dot{m}}_{19}={\dot{m}}_{20}$	${\dot{Ex}}_{19}-{\dot{Ex}}_{20}$	${\dot{Ex}}_1+{\dot{Ex}}_8-{\dot{Ex}}_7$
Pump2	${\dot{W}}_{Pum2}={\dot{m}}_2\left(h_3-h_2\right)$, ${\eta }_{is,Pum2}=\frac{h_{3s}-h_2}{h_3-h_2}$, ${\dot{m}}_2={\dot{m}}_3$	${\dot{W}}_{Pum2}$	${\dot{Ex}}_3-{\dot{Ex}}_2$
Pump1	${\dot{W}}_{Pum1}={\dot{m}}_8\left(h_9-h_8\right)$, ${\eta }_{is,Pum2}=\frac{h_{9s}-h_8}{h_9-h_8}$, ${\dot{m}}_8={\dot{m}}_9$	${\dot{W}}_{Pum1}$	${\dot{Ex}}_9-{\dot{Ex}}_8$
T.V1	$h_6=h_7$, ${\dot{m}}_6={\dot{m}}_7$	${\dot{Ex}}_6$	${\dot{Ex}}_7$
Heat Exchanger1	${\dot{Q}}_{HE1}={\dot{m}}_5\left(h_5-h_6\right)$, ${\dot{Q}}_{HE1}={\dot{m}}_{10}\left(h_{10}-h_9\right)$, ${\epsilon }_{HE1}=\frac{h_{10}-h_9}{h_5-h_9}$, ${\dot{m}}_5={\dot{m}}_6$, ${\dot{m}}_9={\dot{m}}_{10}$	${\dot{Ex}}_5-{\dot{Ex}}_6$	${\dot{Ex}}_{10}-{\dot{Ex}}_9$
Evaporator	${\dot{Q}}_{Eva}={\dot{m}}_4\left(h_4-h_3\right)$, ${\dot{Q}}_{Eva}={\dot{m}}_{23}\left(h_{23}-h_{24}\right)$, ${\dot{m}}_3={\dot{m}}_4$, ${\dot{m}}_{23}={\dot{m}}_{24}$	${\dot{Ex}}_{23}-{\dot{Ex}}_{24}$	${\dot{Ex}}_4-{\dot{Ex}}_3$
Absorber1	${\dot{Q}}_{Abs1}={\dot{m}}_4{h}_4+{\dot{m}}_{10}{h}_{10}-{\dot{m}}_5{h}_5$, ${\dot{Q}}_{Abs1}={\dot{m}}_{11}{h}_{11}+{\dot{m}}_{16}{h}_{16}-{\dot{m}}_{15}{h}_{15}$, ${\dot{m}}_5={\dot{m}}_4+{\dot{m}}_{10}$, ${\dot{m}}_{15}={\dot{m}}_{11}+{\dot{m}}_{16}$	${\dot{Ex}}_4+{\dot{Ex}}_{10}-{\dot{Ex}}_5$	${\dot{Ex}}_{11}+{\dot{Ex}}_{16}-{\dot{Ex}}_{15}$
Turbine	${\dot{W}}_{Tur}={\dot{m}}_{11}\left(h_{11}-h_{12}\right)$, ${\eta }_{is,Pum2}=\frac{h_{11}-h_{12}}{h_{11}-h_{12s}}$, ${\dot{m}}_{11}={\dot{m}}_{12}$	${\dot{Ex}}_{11}-{\dot{Ex}}_{12}$	${\dot{W}}_{Tur}$
Heat Exchanger2	${\dot{Q}}_{HE2}={\dot{m}}_{16}\left(h_{16}-h_{17}\right)$, ${\dot{Q}}_{HE2}={\dot{m}}_{15}\left(h_{15}-h_{14}\right)$, ${\epsilon }_{HE2}=\frac{h_{16}-h_{17}}{h_{16}-h_{14}}$, ${\dot{m}}_{14}={\dot{m}}_{15}$, ${\dot{m}}_{16}={\dot{m}}_{17}$	${\dot{Ex}}_{16}-{\dot{Ex}}_{17}$	${\dot{Ex}}_{15}-{\dot{Ex}}_{14}$
Pump3	${\dot{W}}_{Pum3}={\dot{m}}_{13}\left(h_{14}-h_{13}\right)$, ${\eta }_{is,Pum2}=\frac{h_{14s}-h_{13}}{h_{14}-h_{13}}$, ${\dot{m}}_{13}={\dot{m}}_{14}$	${\dot{W}}_{Pum3}$	${\dot{Ex}}_{14}-{\dot{Ex}}_{13}$
T.V2	$h_{17}=h_{18}$, ${\dot{m}}_{17}={\dot{m}}_{18}$	${\dot{Ex}}_{17}$	${\dot{Ex}}_{18}$
Absorber2	${\dot{Q}}_{Abs2}={\dot{m}}_{12}{h}_{12}+{\dot{m}}_{18}{h}_{18}-{\dot{m}}_{13}{h}_{13}$, ${\dot{Q}}_{Abs2}={\dot{m}}_{21}\left(h_{22}-h_{21}\right)$, ${\dot{m}}_{13}={\dot{m}}_{12}+{\dot{m}}_{18}$, ${\dot{m}}_{13}{X}_{13}={\dot{m}}_{12}{X}_{12}+{\dot{m}}_{18}{X}_{18}$, ${\dot{m}}_{21}={\dot{m}}_{22}$	${\dot{Ex}}_{12}+{\dot{Ex}}_{18}-{\dot{Ex}}_{13}$	${\dot{Ex}}_{22}-{\dot{Ex}}_{21}$

.

In addition, ECOP is exergetic coefficient of performance defined by [39]:

$$ECOP=\frac{Q_{AB}\left(1-\frac{T_0}{T_{AB}}\right)}{Q_{GE}\left(1-\frac{T_0}{T_{GEN}}\right)+Q_{EV}\left(1-\frac{T_0}{T_{EV}}\right)}$$

(12)

3.2. Thermoeconomic Analysis

Based on the gained exergy of the studied systems, the system’s economic evaluation is carried out to assess the cost per exergy unit of the entire cycle. To do so, the cost balance equation is applied to all components of the system. The cost balance relation is expressed by the following relation [37]:

$${\dot{C}}_{P,tot}={\dot{C}}_{F,tot}+{\dot{Z}}_{tot}^{CI}+{\dot{Z}}_{tot}^{OM}$$

(13)

where ${\dot{C}}_P$, ${\dot{C}}_F$, ${\dot{Z}}^{CI}$, and ${\dot{Z}}^{OM}$ are cost rate related to the product, fuel, capital investment, and operating-maintenance of the system, respectively. In the cost balance equation, the cost rates can be written as a function of the cost per unit of exergy (c) for each exergy stream [35]:

$$\dot{C}=c\dot{E}.$$

(14)

The kth component’s total cost rate is equal to the sum of the ${\dot{Z}}_k^{CI}$ and ${\dot{Z}}_k^{OM}$ [35]:

$${\dot{Z}}_k={\dot{Z}}_k^{CI}+{\dot{Z}}_k^{OM}.$$

(15)

The capital investment is converted to the cost rate by applying the following equation [35]:

$${\dot{Z}}_k=CRF\times \frac{{\varphi }_r}{N\times 3600}\times Z_k$$

(16)

Here $Z_k$, ${\varphi }_r$, and $N$ are the cost of kth component purchase, maintenance factor, and number of hours of the unit operation per year, respectively. Furthermore, ${\varphi }_r$ and N are equal to 1.06 and 7000 h, respectively, and CRF stands for capital recovery factor obtained by the following equation [35]:

$$CRF=\frac{i_r{\left(1+i_r\right)}^n}{{\left(1+i_r\right)}^n-1}$$

(17)

where $i_r$ and n are interest rate and the number of years of the unit operation, respectively. The values of $i_r$ and n are 0.15 and 20 years, accordingly.

The system’s total cost is expressed as [35]:

$${\dot{C}}_{tot}=\sum {\dot{C}}_P.$$

(18)

The system’s total SUCP can be written as [40]:

$$SUCP=\frac{{\dot{C}}_{w,net}}{{\dot{W}}_{net}}$$

(19)

where, ${\dot{C}}_{w,net}$ is the cost rate of the net power production. The required cost balance and other auxiliary equations to appraise the proposed system are listed in

Table 3. Cost balance, auxiliary, and equipment cost equations applied to each component of the: (a) AHT/KC and (b) AHT/APC.

Component	Cost Balance Equations	Auxiliary Equations	Equipment Cost
(a) AHT/KC
Condenser1	${\dot{C}}_1+{\dot{C}}_{25}+{\dot{Z}}_{Cond1}={\dot{C}}_2+{\dot{C}}_{28}$	$c_{25}=0$ $c_1=c_2$	$Z_{Cond1}=130{\left(\frac{A_{Cond1}}{0.093}\right)}^{0.78}$
Generator	${\dot{C}}_7+{\dot{C}}_{27}+{\dot{Z}}_{Gen}={\dot{C}}_1+{\dot{C}}_8+{\dot{C}}_{28}$	$c_{27}=15.24$ $c_{27}=c_{28}$ $\frac{{\dot{C}}_1}{{\dot{m}}_1\left(e{x}_1-e{x}_7\right)}-\frac{{\dot{C}}_7\left(e{x}_8-e{x}_1\right)}{{\dot{m}}_7\left(e{x}_1-e{x}_7\right)\left(e{x}_8-e{x}_7\right)}-\frac{{\dot{C}}_8}{{\dot{m}}_8\left(e{x}_8-e{x}_7\right)}=0$	$Z_{Gen}=130{\left(\frac{A_{Gen}}{0.093}\right)}^{0.78}$
Pump2	${\dot{C}}_2+{\dot{C}}_{Pum2}+{\dot{Z}}_{Pum2}={\dot{C}}_3$	$c_{Pum2}=c_{Tur}$	$Z_{Pum2}=3540{\left({\dot{W}}_{Pum2}\right)}^{0.71}$
Pump1	${\dot{C}}_8+{\dot{C}}_{Pum1}+{\dot{Z}}_{Pum1}={\dot{C}}_9$	$c_{Pum1}=c_{Tur}$	$Z_{Pum1}=3540{\left({\dot{W}}_{Pum1}\right)}^{0.71}$
T.V1	${\dot{C}}_6+{\dot{Z}}_{T.V1}={\dot{C}}_7$	$-$	$Z_{T.V1}=114.5{\dot{m}}_8$
Heat Exchanger	${\dot{C}}_5+{\dot{C}}_9+{\dot{Z}}_{HE1}={\dot{C}}_6+{\dot{C}}_{10}$	$c_5=c_6$	$Z_{HE}=130{\left(\frac{A_{HE}}{0.093}\right)}^{0.78}$
Evaporator	${\dot{C}}_3+{\dot{C}}_{23}+{\dot{Z}}_{Eva}={\dot{C}}_4+{\dot{C}}_{24}$	$c_{23}=15.24$ $c_3=c_4$	$Z_{Eva}=130{\left(\frac{A_{Eva}}{0.093}\right)}^{0.78}$
Absorber	${\dot{C}}_4+{\dot{C}}_{10}+{\dot{C}}_{20}+{\dot{Z}}_{Abs}={\dot{C}}_5+{\dot{C}}_{11}$	$\frac{{\dot{C}}_4+{\dot{C}}_{10}}{{\dot{Ex}}_4+{\dot{Ex}}_{10}}=\frac{{\dot{C}}_5}{{\dot{Ex}}_5}$	$Z_{Abs}=130{\left(\frac{A_{Abs}}{0.093}\right)}^{0.78}$
Separator	${\dot{C}}_{11}+{\dot{Z}}_{Sep}={\dot{C}}_{12}+{\dot{C}}_{13}$	$c_{12}=c_{13}$	$Z_{Sep}=0$
Turbine	${\dot{C}}_{12}+{\dot{Z}}_{Tur}={\dot{C}}_{16}+{\dot{C}}_{Tur}$	$c_{12}=c_{16}$	$Z_{Tur}=4405{\left({\dot{W}}_{Tur}\right)}^{0.7}$
Regenerator	${\dot{C}}_{13}+{\dot{C}}_{19}+{\dot{Z}}_{Reg}={\dot{C}}_{14}+{\dot{C}}_{20}$	$c_{13}=c_{14}$	$Z_{Reg}=130{\left(\frac{A_{Reg}}{0.093}\right)}^{0.78}$
T.V2	${\dot{C}}_{14}+{\dot{Z}}_{T.V2}={\dot{C}}_{15}$	$-$	$Z_{T.V2}=114.5{\dot{m}}_{14}$
Mixer	${\dot{C}}_{15}+{\dot{C}}_{16}+{\dot{Z}}_{Mix}={\dot{C}}_{17}$	$-$	$Z_{Mix}=2$
Pump3	${\dot{C}}_{18}+{\dot{C}}_{Pum3}+{\dot{Z}}_{Pum3}={\dot{C}}_{19}$	$c_{Pum3}=c_{Tur}$	$Z_{Pum3}=3540{\left({\dot{W}}_{Pum3}\right)}^{0.71}$
Condenser2	${\dot{C}}_{17}+{\dot{C}}_{21}+{\dot{Z}}_{Cond2}={\dot{C}}_{18}+{\dot{C}}_{22}$	$c_{21}=0$ $c_{17}=c_{18}$	$Z_{Cond2}=130{\left(\frac{A_{Cond2}}{0.093}\right)}^{0.78}$
(b) AHT/APC
Condenser	${\dot{C}}_1+{\dot{C}}_{25}+{\dot{Z}}_{Cond2}={\dot{C}}_2+{\dot{C}}_{26}$	$c_{25}=0$ $c_1=c_2$	$Z_{Cond}=130{\left(\frac{A_{Cond}}{0.093}\right)}^{0.78}$
Generator	${\dot{C}}_7+{\dot{C}}_{19}+{\dot{Z}}_{Gen}={\dot{C}}_1+{\dot{C}}_8+{\dot{C}}_{20}$	$c_{19}=15.24$ $c_{19}=c_{20}$ $\frac{{\dot{C}}_1}{{\dot{m}}_1\left(e{x}_1-e{x}_7\right)}-\frac{{\dot{C}}_7\left(e{x}_8-e{x}_1\right)}{{\dot{m}}_7\left(e{x}_1-e{x}_7\right)\left(e{x}_8-e{x}_7\right)}-\frac{{\dot{C}}_8}{{\dot{m}}_8\left(e{x}_8-e{x}_7\right)}$	$Z_{Gen}=130{\left(\frac{A_{Gen}}{0.093}\right)}^{0.78}$
Pump2	${\dot{C}}_2+{\dot{C}}_{Pum2}+{\dot{Z}}_{Pum2}={\dot{C}}_3$	$c_{Pum2}=c_{Tur}$	$Z_{Pum2}=3540{\left({\dot{W}}_{Pum2}\right)}^{0.71}$
Pump1	${\dot{C}}_8+{\dot{C}}_{Pum1}+{\dot{Z}}_{Pum1}={\dot{C}}_9$	$c_{Pum1}=c_{Tur}$	$Z_{Pum1}=3540{\left({\dot{W}}_{Pum1}\right)}^{0.71}$
T.V1	${\dot{C}}_6+{\dot{Z}}_{T.V1}={\dot{C}}_7$	$-$	$Z_{T.V1}=114.5{\dot{m}}_8$
Heat Exchanger1	${\dot{C}}_5+{\dot{C}}_9+{\dot{Z}}_{HE1}={\dot{C}}_6+{\dot{C}}_{10}$	$c_5=c_6$	$Z_{HE1}=130{\left(\frac{A_{HE1}}{0.093}\right)}^{0.78}$
Evaporator	${\dot{C}}_3+{\dot{C}}_{23}+{\dot{Z}}_{Eva}={\dot{C}}_4+{\dot{C}}_{24}$	$c_{23}=15.24$ $c_3=c_4$	$Z_{Eva}=130{\left(\frac{A_{Eva}}{0.093}\right)}^{0.78}$
Absorber1	${\dot{C}}_4+{\dot{C}}_{10}+{\dot{C}}_{15}+{\dot{Z}}_{Abs1}={\dot{C}}_5+{\dot{C}}_{11}+{\dot{C}}_{16}$	$\frac{{\dot{C}}_4+{\dot{C}}_{10}}{{\dot{Ex}}_4+{\dot{Ex}}_{10}}=\frac{{\dot{C}}_5}{{\dot{Ex}}_5}$	$Z_{Abs1}=130{\left(\frac{A_{Abs1}}{0.093}\right)}^{0.78}$
Turbine	${\dot{C}}_{11}+{\dot{Z}}_{Tur}={\dot{C}}_{12}+{\dot{C}}_{Tur}$	$c_{11}=c_{12}$	$\left(\frac{1536{\dot{m}}_{11}}{0.92-{\eta }_{is,Tur}}\right)Ln\left(\frac{P_{11}}{P_{12}}\right)\left(1+e^{0.036T_{11}-54.4}\right)$
Heat Exchanger2	${\dot{C}}_{14}+{\dot{C}}_{16}+{\dot{Z}}_{HE2}={\dot{C}}_{15}+{\dot{C}}_{17}$	$c_{16}=c_{17}$	$Z_{HE2}=130{\left(\frac{A_{HE2}}{0.093}\right)}^{0.78}$
Pump3	${\dot{C}}_{13}+{\dot{C}}_{Pum3}+{\dot{Z}}_{Pum3}={\dot{C}}_{14}$	$c_{Pum3}=c_{Tur}$	$Z_{Pum3}=3540{\left({\dot{W}}_{Pum3}\right)}^{0.71}$
T.V2	${\dot{C}}_{17}+{\dot{Z}}_{T.V2}={\dot{C}}_{18}$	$-$	$Z_{T.V2}=114.5{\dot{m}}_{17}$
Absorber2	${\dot{C}}_{12}+{\dot{C}}_{18}+{\dot{C}}_{21}+{\dot{Z}}_{Abs2}={\dot{C}}_{13}+{\dot{C}}_{22}$	$c_{21}=0$ $\frac{{\dot{C}}_{12}+{\dot{C}}_{18}}{{\dot{Ex}}_{12}+{\dot{Ex}}_{18}}=\frac{{\dot{C}}_{13}}{{\dot{Ex}}_{13}}$	$Z_{Abs2}=130{\left(\frac{A_{Abs2}}{0.093}\right)}^{0.78}$

. The unit cost of heat sources is an important parameter in determining the cost of products, which is assumed 15.24 $/GJ in this investigation [41]. Furthermore, the overall heat transfer coefficient for heat exchangers is presented in

Table 4. The overall heat transfer coefficient for heat exchangers [33,37].

Component	U (kW m−2 K−1)
Absorber	0.6
Condenser	1.1
Evaporator	1.5
Generator	1.6
Heat Exchanger	1
Regenerator	1

.

4. Model Validation

To elucidate the authenticity of the mathematical modeling for various components of the proposed systems, it is vital to validate the results of the present study with the outcomes of published literature. Considering this aim, the AHT cycle, KC, and APC are chosen as benchmarks, and the results are validated as follows. AHT is verified with the results of Ref. [38]. In Figure 2, the obtained COP from the present analysis is compared with that of Best et al. [38] under an equal situation. Figure 2 displays COP of AHT versus absorber temperature at three different temperatures of the condenser. According to Figure 2, the results of the present study and those of Ref. [38] are close to each other.

To validate the employed equations and accuracy of the procedure in the KC, the thermal efficiency and turbine power at different ammonia concentrations obtained by the present study are compared with those reported by He et al. [40]. Figure 3 displays the accuracy of the employed mathematical modeling to simulate the KC.

Furthermore, the APC is simulated, and thermal efficiency, mass flow rate across the turbine, and steam generator thermal power are validated by using the outcomes of Ref. [42]. According to the information revealed in

Table 5. Results of the simulation of the APC between the current study and Shokati et al. [42].

Parameter	Present Work	Ref.	Relative Error (%)
First law efficiency (%)	10.69	10.71	0.19
Mass flow rate across turbine (kg s−1)	4.26	4.356	2.2
Steam generator thermal power (MW)	9.387	9.335	0.56

, a subtle discrepancy is seen between the results of the current investigation and Ref. [42].

5. Results and Discussion

Thermodynamic properties and costs of the streams for the AHT/KC cycle and AHT/APC cycle are presented in

Table 6. Thermodynamic properties and costs of the streams for the AHT/KC.

State	Fluid	T (K)	P (bar)	X (-)	h (kJ kg−1)	s (kJ kg−1 K−1)	$\dot{\mathit{m}}$ (kg s−1)	$\dot{\mathit{E}\mathit{x}}\left(\mathbf{kW}\right)$	$\dot{\mathit{C}}$ ($ yr−1)	c ($ GJ−1)
1	Ammonia	358	10.03	1	1646	5.816	0.717	239	212,800	28.24
2	Ammonia	298.2	10.03	1	317.7	1.409	0.717	229	203,904	28.24
3	Ammonia	299.3	45.94	1	324.7	1.412	0.717	233.2	220,141	29.93
4	Ammonia	358	45.94	1	1468	4.681	0.717	254.2	334,292	29.93
5	Ammonia-Water	403.1	45.94	0.548	380.9	1.647	2.738	314.7	414,931	41.8
6	Ammonia-Water	379.4	45.94	0.548	258.2	1.334	2.738	234.8	309,586	41.8
7	Ammonia-Water	341.4	10.03	0.548	258.2	1.381	2.738	195.8	309,652	50.14
8	Ammonia-Water	358	10.03	0.3876	152.4	1.06	2.021	54.46	165,335	96.28
9	Ammonia-Water	358.7	45.94	0.3876	157.6	1.062	2.021	63.66	198,406	98.83
10	Ammonia-Water	394.3	45.94	0.3876	323.7	1.503	2.021	133.5	308,600	73.32
11	Ammonia-Water	384.3	15	0.4	401.6	1.723	3.208	259.6	590,549	72.15
12	Ammonia-Water	384.3	15	0.9327	1570	4.962	0.2955	117.9	268,356	72.15
13	Ammonia-Water	384.3	15	0.346	283	1.395	2.912	141.6	322,194	72.15
14	Ammonia-Water	313.3	15	0.346	−33.69	0.4848	2.912	9.459	21,522	72.15
15	Ammonia-Water	313	2.062	0.346	−33.69	0.4895	2.912	5.372	21,593	127.5
16	Ammonia-Water	313.5	2.062	0.9327	1295	5.059	0.2955	28.07	63,859	72.15
17	Ammonia-Water	313.1	2.062	0.4	88.72	0.9105	3.208	33.44	85,452	81.02
18	Ammonia-Water	303.1	2.062	0.4	−94.68	0.3178	3.208	11.93	30,493	81.02
19	Ammonia-Water	303.3	15	0.4	−92.91	0.3187	3.208	16.77	48,743	92.19
20	Ammonia-Water	367.6	15	0.4	194.6	1.178	3.208	117.5	354,280	95.59
21	Water	298.2	1.013	−	104.8	0.3669	46.88	0	0	0
22	Water	301.2	1.013	−	117.4	0.4088	46.88	2.94	59,637	643.2
23	Water	363.2	2.5	−	377.1	1.192	19.52	509.9	245,039	15.24
24	Water	353.2	2.5	−	335.1	1.075	19.52	372.6	133,141	11.33
25	Water	293.2	1.013	−	83.93	0.2962	15.18	2.692	0	0
26	Water	308.2	1.013	−	146.7	0.5049	15.18	10.41	13,908	42.35
27	Water	363	2.5	−	376.4	1.191	10	260	124,970	15.24
28	Water	344.4	2.5	−	298.3	0.9698	10	137.5	66,097	15.24

and

Table 7. Thermodynamic properties and costs of the streams for the AHT/APC.

State	Fluid	T (K)	P (bar)	X (-)	h (kJ kg−1)	s (kJ kg−1 K−1)	$\dot{\mathit{m}}$ (kg s−1)	$\dot{\mathit{E}\mathit{x}}\left(\mathbf{kW}\right)$	$\dot{\mathit{C}}$ ($ yr−1)	c ($ GJ−1)
1	Ammonia	358	10.03	1	1646	5.816	0.717	239	209,826	27.84
2	Ammonia	298.2	10.03	1	317.7	1.409	0.717	229	201,054	27.84
3	Ammonia	299.3	45.94	1	324.7	1.412	0.717	233.2	215,351	29.28
4	Ammonia	358	45.94	1	1468	4.681	0.717	254.2	327,018	29.28
5	Ammonia-Water	403.1	45.94	0.548	380.9	1.647	2.738	314.7	399,705	40.27
6	Ammonia-Water	379.4	45.94	0.548	258.2	1.334	2.738	234.8	298,225	40.27
7	Ammonia-Water	341.4	10.03	0.548	258.2	1.381	2.738	195.8	298,292	48.3
8	Ammonia-Water	358	10.03	0.3876	152.4	1.06	2.021	54.46	156,950	91.39
9	Ammonia-Water	358.7	45.94	0.3876	157.6	1.062	2.021	63.66	185,955	92.63
10	Ammonia-Water	394.3	45.94	0.3876	323.7	1.503	2.021	133.5	292,282	69.45
11	Ammonia	384.3	12	1	1705	5.893	0.2893	106.9	217,094	64.39
12	Ammonia	293.7	3.239	1	1522	5.963	0.2893	47.99	97,437	64.39
13	Ammonia-Water	316.1	3.239	0.4	−37.41	0.5024	2.047	12.21	29,588	76.83
14	Ammonia-Water	316.3	12	0.4	−36.2	0.5029	2.047	14.35	36,936	81.65
15	Ammonia-Water	362.5	12	0.4	170.9	1.114	2.047	65.46	281,188	136.2
16	Ammonia-Water	384.3	12	0.3012	296.2	1.407	1.757	83.61	291,212	110.4
17	Ammonia-Water	329.9	12	0.3012	54.98	0.7312	1.757	14.09	49,084	110.4
18	Ammonia-Water	330	3.239	0.3012	54.98	0.7342	1.757	12.5	49,126	124.6
19	Water	363	2.5	−	376.4	1.191	10	260	124,970	15.24
20	Water	344.4	2.5	−	298.3	0.9698	10	137.5	66,097	15.24
21	Water	298.2	1.013	−	104.8	0.3669	14.67	0	0	0
22	Water	308.2	1.013	−	146.7	0.5049	14.67	10.06	120,774	380.5
23	Water	363.2	2.5	−	377.1	1.192	19.52	509.9	245,039	15.24
24	Water	353.2	2.5	−	335.1	1.075	19.52	372.6	135,625	11.54
25	Water	293.2	1.013	−	83.93	0.2962	15.18	2.692	0	0
26	Water	308.2	1.013	−	146.7	0.5049	15.18	10.41	13,784	41.97

, respectively. These properties are temperature, pressure, ammonia concentration, enthalpy, entropy, mass flow rate, total exergy rate, cost rate, and cost per exergy unit.

Table 8. Component cost rates and exergoeconomic factors for the: (a) AHT/KC and (b) AHT/APC.

Component	${\dot{\mathit{E}\mathit{x}}}_{\mathit{D},\mathit{k}}\left(\mathbf{kW}\right)$	${\dot{\mathit{C}}}_{\mathit{D},\mathit{k}}(\${\mathbf{yr}}^{-1})$	${\dot{\mathit{Z}}}_{\mathit{k}}(\${\mathbf{yr}}^{-1})$	${\mathit{\eta }}_{\mathit{e}\mathit{x},\mathit{k}}(\%)$	${\mathit{f}}_{\mathit{k}}(\%)$	${\mathit{r}}_{\mathit{k}}(\%)$
(a) AHT/KC
Condenser1	2.268	4084	5012	77.3	55.1	102.2
Generator	24.91	17,484	9611	79.66	35.47	46.02
Pump2	0.75	2854	2358	85.05	45.24	37.55
Pump1	1.311	4712	3987	87.53	45.83	29.91
T.V1	38.99	61,644	66.45	83.4	0.1077	19.93
Heat Exchanger	10.11	15,957	4848	87.35	23.3	19.75
Evaporator	16.34	15,421	2253	88.1	12.75	15.8
Absorber	30.88	51,365	8308	82.14	13.92	26.18
Separator	0	0	0	100	0	0
Turbine	8.623	23,851	20,279	90.41	45.95	21.58
Regenerator	31.39	95,194	4866	76.24	4.863	33.28
T.V2	4.087	16,429	70.67	56.79	0.4283	76.66
Mixer	0	0	0	100	0	0
Pump3	0.8359	3157	2571	85.25	44.89	36.53
Condenser2	18.57	376,634	4678	13.67	1.227	693.8
(b) AHT/APC
Condenser	2.268	4048	5012	77.3	55.32	103.3
Generator	24.91	17,484	9611	79.66	35.47	46.02
Pump2	0.75	2513	2358	85.05	48.41	40.8
Pump1	1.311	4133	3987	87.53	49.1	32.46
T.V1	38.99	59,382	66.45	83.4	0.1118	19.93
Heat Exchanger1	10.11	15,397	4848	87.35	23.95	19.95
Evaporator	16.34	15,086	2253	88.1	12.99	15.85
Absorber1	47.84	86,866	7523	72.33	7.97	42.98
Turbine	6.053	14,404	6166	89.73	29.98	17.19
Heat Exchanger2	18.41	87,966	2124	73.52	2.357	37.21
Pump3	0.3519	1212	1432	85.85	54.17	44.69
T.V2	1.594	6266	42.64	88.69	0.6759	12.85
Absorber2	38.21	458,542	3799	20.85	0.8216	395.2

presents some significant exergy factors including exergy destruction rate (${\dot{Ex}}_{D,k}$), cost of exergy destruction rate (${\dot{C}}_{D,k}$), investment cost (${\dot{Z}}_k$), exergy efficiency (${\eta }_{ex,k}$), exergoeconomic factor ($f_k$), and relative cost difference ($r_k$) for different components of the proposed cycles. As it is clear, throttling valve 1 in the AHT/KC cycle and absorber 1 in the AHT/APC cycle account for the highest exergy destruction among all components, with 38.99 kW and 47.84 kW, respectively.

Another indication of Table 8 is that the highest cost of exergy destruction among all components belongs to condenser 2 in the AHT/KC cycle and absorber 2 in the AHT/APC cycle. As expected, among all constituents, the turbine in the AHT/KC cycle and the generator in the AHT/APC cycle have the highest investment cost, respectively. In addition, the investment cost pertaining to the mixer and separator in the AHT/KC cycle and the throttling valves is the lowest since the pressure drop through these components is the lowest as well.

Table 9. Thermodynamic and thermoeconomic evaluation results obtained from the simulation of AHT/KC.

Performance Parameters	Unit	Amount
CR	−	3.819
COP	−	0.4108
ECOP	−	0.6107
$\mathrm{Net}\mathrm{power}\mathrm{output}\left({\dot{W}}_{net}\right)$	kW	60.06
$\mathrm{Cooling}\mathrm{capacity}\left({\dot{Q}}_{Eva}\right)$	kW	0.82
$\mathrm{First}-\mathrm{law}\mathrm{efficiency}\left({\eta }_{th,overall}\right)$	%	7.69
$\mathrm{Second}-\mathrm{law}\mathrm{efficiency}\left({\eta }_{ex,overall}\right)$	%	49.03
Total SUCP of system (SUCPtot)	$ GJ−1	87.72

and

Table 10. Thermodynamic and thermoeconomic evaluation results obtained from the simulation of AHT/APC.

Performance Parameters	Unit	Amount
CR	−	3.819
COP	−	0.4108
ECOP	−	0.6107
$\mathrm{Net}\mathrm{output}\mathrm{power}\left({\dot{W}}_{net}\right)$	kW	34.86
$\mathrm{Cooling}\mathrm{capacity}\left({\dot{Q}}_{Eva}\right)$	kW	0.82
$\mathrm{First}-\mathrm{law}\mathrm{efficiency}\left({\eta }_{th,overall}\right)$	%	4.464
$\mathrm{Second}-\mathrm{law}\mathrm{efficiency}\left({\eta }_{ex,overall}\right)$	%	28.46
Total SUCP of system (SUCPtot)	$ GJ−1	75.45

represent the results of the energy, exergy, and exergoeconomic analysis obtained for the proposed cycles. The results demonstrate that the maximum net output power is achieved for the AHT/KC cycle, with 60.06 kW. However, the maximum thermal and exergy efficiencies are gained in the AHT/KC cycle, with 7.69% and 49.03%, respectively. The SUCP of the overall system in the AHT/KC cycle and AHT/APC cycle is assessed 87.72 $/GJ and 75.45 $/GJ, respectively.

According to Table 8, the maximum exergy destruction rate $\left({\dot{Ex}}_{D,k}\right)$ for the AHT/KC is related to throttle vale 1 followed by the regenerator. For the AHT/APC, absorber 1 has the maximum contribution to the exergy destruction rate.

6. Parametric Study

In this section, the effect of key variables on the performance of the designed power cycles is studied.

6.1. The Effect of Generator Temperature

Figure 4 shows the effect of the generator temperature on the SUCP as well as the net output power of the AHT/KC and AHT/APC cycles. According to this figure, the net power of both systems increases with a rise in the temperature of the generator. This comes from the fact that the heat transferred to KC and APC in the absorber increases by the generator temperature rise, and consequently, the net power of the systems produced by the turbine goes up. On the other hand, due to the increased net output power, the SUCP of the system decreases with the enhancement of the generator temperature. Figure 4 shows that AHT/KC produces more power than AHT/APC.

The effect of generator temperature on the energy and exergy efficiencies of both AHT/KC and AHT/APC is depicted in Figure 5. As can be observed, by augmentation of the energy and exergy efficiencies, the generator temperature rises. This improvement is the direct result of net power enhancement. From both the first and second laws of thermodynamics viewpoint, AHT/KC has a better performance in comparison with AHT/APC.

Figure 6 depicts the generator temperature effect on the CR, COP, and ECOP for the AHT/KC and AHT/APCs. When the temperature increases, the mass flow rate of the refrigerant/absorbent solution decreases, leading to a decrease in the CR. Additionally, by the elevation of the generator outlet temperature, the amount of heat production for the AHT increases, which results in the increment of COP. In fact, CR and heat production in the absorber are inversely proportional. According to the figure, ECOP reaches its maximum value at the temperature of 355 K.

6.2. Effect of Absorber Temperature

Figure 7 shows the effect of absorber/absorber1 outlet temperature on the total SUCP and net output power of the proposed combined systems. By the augmentation of the absorber outlet temperature in the AHT, first, the output power of the turbine in the KC increases. Next, it takes the reverse direction, resulting in a stage of increase followed by a decrease in the net output power in the KC. The total SUCP of the system, as a result, first decreases and then increases. Moreover, for the AHT, with the increase in the outlet temperature of the absorber, the turbine output power decreases in the APC. So, the net output power decreases, which leads to the increased total SUCP of the system in the APC. According to Figure 7, the KC produces maximum power at the absorber outlet temperature of 400 K.

Figure 8 demonstrates the effect of outlet temperature of absorber/absorber1 on the thermal and exergy efficiencies of the AHT/KCs and AHT/APCs. According to the figure, as the absorber outlet temperature in the AHT increases, the net output power in the KC first rises and then falls, leading to a stage of increase and decrease in the thermal and exergy efficiencies of the cycle. Additionally, for the APCs, the net output power decreases and causes the decrement of thermal and exergy efficiencies. It is obvious that thermal and exergy efficiencies of the AHT/KCs are higher than those of the AHT/APC.

The effect of the outlet temperature of absorber/absorber1 on the CR, COP, and ECOP of the proposed integrated power cycles is illustrated in Figure 9. With an increase in the absorber outlet temperature of the AHT, the mass flow rate of refrigerant/absorbent solution increases at the inlet of the generator, and the mass flow of refrigerant decreases at the generator outlet. Accordingly, a higher CR occurs. Furthermore, the increased absorber outlet temperature corresponds with the decreased heat production in the absorber for the AHT, leading to a decrease in the COP of the cycle. The figure also shows that ECOP goes up to reach a maximum value and then goes downward.

6.3. Effect of Absorber Pressure

Figure 10 illustrates the impact of outlet pressure of absorber/absorber1 on the total SUCP and net output power of the proposed power cycles. With the increase of the absorber outlet pressure in the KC as well as outlet pressure of the absorber1 in the APC, the turbine output power takes higher values gradually and then undergoes a reverse trend. Therefore, the net output power first increases and then decreases, resulting in a reduction and enhancement in the magnitude of the total SUCP of the system, respectively.

Figure 11 demonstrates the effect of outlet pressure of absorber/absorber1 on the thermal and exergy efficiencies of the AHT/KCs and AHT/APCs. According to the plots, with the increase in the absorber outlet pressure in the KC and by the elevation of the outlet pressure of absorber1 in the APC, the net output power of the cycle first increases and then decreases. Hence, the thermal and exergy efficiencies of the cycle indicate the same trend. The figure shows that the thermal and exergy efficiencies of the AHT/KCs are higher than those of the AHT/APC.

6.4. Effect of Ammonia Concentration

The effect of basic ammonia concentration on the total SUCP and net output power of the system is shown in Figure 12. For the KC, an increase in the concentration of ammonia results in an increase followed by a decrease in turbine output power. Accordingly, the net output power of the cycle goes upward and then returns downward. Thus, the SUCP shows the opposite trend of descending and then ascending by the increment of concentration of ammonia. For the APC, the net output power of the turbine shows a negative inclination versus the ammonia concentration rise, and as a result, the net output power decrease, and the total SUCP of the system increases.

Figure 13 shows the effect of basic ammonia concentration on the thermal and exergy efficiencies of the proposed cycles. Since increasing the concentration of ammonia causes the net output power to first rise and fall afterward, the first and second law efficiencies take the same trend of going up and down. Furthermore, in the APC, due to the decreased net output power, both the thermal and exergy efficiencies decrease. According to the figure, the efficiencies of the AHT/KCs are higher than those of AHT/APCs.

6.5. Effect of Condenser 2 Temperature

The thermal and exergy efficiencies, net output power, and total SUCP of the systems as a function of the outlet temperature of condenser2 are illustrated in Figure 14. The figure shows that an increase in the condenser outlet temperature of the KC leads to lower turbine output power and accordingly lower net output power (${\dot{W}}_{net}$). On the other hand, both the ${\dot{C}}_{W,net}$ and ${\dot{W}}_{net}$ decrease with the rise of condenser outlet temperature, but due to a more noticeable decrease of the ${\dot{C}}_{W,net}$, the total SUCP of the system also decreases. It is also visible that the thermal and exergy efficiencies are reduced because of decreased net output power.

6.6. Effect of Absorber 2 Temperature

Figure 15 depicts the effect of outlet temperature of absorber2 on the total SUCP, net output power, and thermal and exergy efficiencies of the suggested integrated power cycles. When the absorber outlet temperature of the APC increases, the output power of the turbine and so the net output power (${\dot{W}}_{net}$) decrease. Another deduction from Figure 15 is that for higher values of absorber temperature, the total SUCP takes lower values. This is because ${\dot{C}}_{W,net}$ decreases by a higher order of magnitude compared with ${\dot{W}}_{net}$. Furthermore, due to the decreased net output power, the thermal and exergy efficiencies of the cycles take a downward inclination.

7. Conclusions

In this study, two novel integrated power cycles of AHT/KC and AHT/APC are recommended. The cycles are driven by low-temperature heat sources. The AHT is used to convert the low-temperature heat sources to high-temperature heat sources. Energetic and exergetic analyses are carried out to evaluate the performance of each cycle based on the first and second laws of thermodynamics. In addition, sensitivity analysis for some different key parameters of cycles is carried out. Some of the main concluded results are summarized here as follows:

• The maximum value of the thermal efficiency belongs to the AHT/KC cycle with 7.69%.
• The maximum exergy efficiency is calculated 49.03% for the AHT/KC cycle.
• The maximum exergy destruction rate in the AHT/KC and AHT/APC is related to throttle valve 1 and absorber 1, respectively.
• Among all components, the turbine in the AHT/KC cycle and the generator in the AHT/APC cycle have the highest investment cost, respectively. In addition, the investment cost associated with the mixer and separator in the AHT/KC cycle and the throttling valves is the lowest one.
• The energetic performance of the proposed power cycles improves with the rise of generator temperature, while it decreases with condenser temperature. Furthermore, it has a polynomial trend with absorber temperature, absorber pressure, and ammonia concentration.
• From the exergy perspective, the cycles’ efficiency is boosted with the rise of generator temperature and is decreased with the increment of ammonia concentration and condenser and absorber temperature.

8. Future Work

In the next study, optimization of the proposed systems will be conducted. Furthermore, modification of the proposed systems can be investigated by employing other cycles in order to improve the overall performance of the proposed systems more considerably.