تحلیل انرژی و اگزرژی یک سیستم تولید سه‌گانه جدید با محرک انرژی زمین گرمایی و بهره‌گیری از مخلوط‌های دو جزئی

Abstract
The two-level cooling output is the main framework of the bi-evaporator technology by which the refrigeration cycles’ capability enhances. Hence, the current study is motivated to assess the feasibility of thermal energy utilization of geothermal energy for an innovative trigeneration system encompassing a bi-evaporator-based refrigerator, a heating terminal, an electricity generation setup. In this paper, a tri-generation system of cooling, heating, and power generation is proposed, which can simultaneously produce all three outputs. The Rankine cycle is combined with an improved ejector refrigeration cycle, where the outlet flow from the second evaporator creates suction in the ejector and activates the ejector refrigeration cycle. In addition, binary working fluids are used instead of pure working fluids to enhance the system's performance. The proposed system is thermodynamically analyzed based on the first and second laws of thermodynamics for various mixtures. The highest power, refrigeration capacity, and heating output are found to be 33 kW, 214 kW, and 306 kW, respectively, for the R236fa/Pentane mixture. Additionally, the highest energy and exergy efficiencies are 54.7% and 27.48%, respectively, for the R142b/Pentane mixture.

Introduction
Refrigeration cycles with extensive uses in various applications such as industrial and domestic sectors and preserving agricultural products, food, and pharmaceutical products are the most attractive option to comfort human life in different dimensions. This challenge motivates researchers to conduct more studies on developing newly devised refrigeration cycles, employing such systems within tri-generation setups, and analyzing their capabilities. Meanwhile, establishing renewable energy-based tri-generation plans to meet energy demand, particularly cooling, can have a great influence on the future of the energy conversion field, covering the rapid growth in energy consumption throughout the world.
Regarding the advantage of bi-evaporator technologies, there seems to be a potential for utilizing bi-evaporator technologies with tri-generation systems via geothermal energy as an instigator. Hence, this survey suggests a novel geothermal-powered tri-generation plant w with a modified Combined Cooling, Heating, and Power (CCHP) generation setup. Following is a list of this survey's most important novelties and works.:
• The proposal of a novel geothermal-based tri-generation plant embracing a newly devised compression/ejection cooling production cycle framework utilizing zeotropic mixtures.
• The modification of previous bi-evaporator refrigeration cycles using an ejector, regenerator, and coherent management of components to reduce wasted energy and boost the whole setup's proficiency.
• The use of energy and exergy methods to access the devised system thermodynamically.
• Conducting a sensitivity study to better understand the impact of design parameters on the performance parameters of the system.

Methodology
Figure 1 shows the newly devised geothermal tri-generation system in this paper. Indeed, using the zeotropic mixtures, the CCHP utilizes a bi-evaporator technology with two levels of cooling temperature, i.e., ordinary cooling and freezing temperatures. Likewise, the structure processes produce heat and electricity via a heating device and an organic turbine.
Generally, the geothermal water flows into the CCHP system through the vapor generator. In the CCHP unit, the cold stream of the zeotropic mixture (state 12) is heated by the vapor generator and leaves at state 1 to flow into the organic turbine. After generating power, stream 2, i.e., the turbine's output, enters into the condenser and loses its heat completely at state 3. Stream 3 is divided into two parts, one of which stream 4 uses in the bi-evaporator system. For this purpose, streams 13 and 4 flow into expansion valves 2 and 3 to generate freezing and ordinary cooling via evaporators 1 and 2, respectively. Simply put, the output streams of these components are mixed through the ejector, where stream 7 (the output of evaporator 2) is the primary and stream 15 (the output of evaporator 1) is the secondary stream of the ejector. Hence, the compressor pressures the stream leaving the ejector (state 9); therefore, the heating production heater can generate heat. Accordingly, streams 10 and 17 (pumped by pump 1) are mixed at state 11, where pump 2 pumps this stream into the vapor generator for recycling.

Figure1. The layout of the newly devised geothermal-driven tri-generation system
MATLAB software has been utilized to simulate the proposed, considering its abilities involving fundamental thermodynamic relations and fluid property library to code the modeling steps. The first and second laws of thermodynamics in terms of mass, energy, and exergy are used in the present study as follows (Feili et al. 2022):

(1)

(2)
(3)
Using the above formulations, each component of the proposed system is analyzed, and finally, the amounts of generated commodities are obtained.
The overall performance metrics parameters, including Energy and exergy efficiencies of the newly devised tri-generation setup, are articulated respectively:

(4)

(5)
Conclusion
This study presents a tri-generation cooling, heating, and electricity system based on binary mixtures as working fluids. The performance of this system, which is obtained by integrating the organic Rankine cycle with the ejector refrigeration cycle, has been analyzed and investigated with different combinations of mixtures from the perspective of the first and second laws of thermodynamics. Some important results are as follows:
• As a significant finding, unlike pure fluids, the phase change process of two-phase mixtures does not occur at a constant temperature. This temperature change during the heat exchangers' phase change process leads to better temperature matching and performance improvement for two-phase mixtures compared to pure fluids.
• By examining different mixtures, it was found that the R142b/Pentane mixture has the highest temperature change during the phase change process, heat capacity, and energy efficiency, approximately at mass fractions of 50%, 80%, and 70%, respectively. The R236fa/Pentane mixture also has the highest net electricity generation and refrigeration capacity, approximately at mass fractions of 50% and 85%, respectively.
• Energy efficiency at a mass fraction of 72% R142b has a maximum value of 54.76%, while for pure fluid, this value is 50.86%.
• Exergy efficiency at a mass fraction of 50% R142b has a maximum value of 27.48%, while for pure fluid, it is 16.31%.
Keywords
Renewable energy; Zeotropic mixture; tri-generation; Organic cycle; Ejector refrigeration cycle


Abstract
The two-level cooling output is the main framework of the bi-evaporator technology by which the refrigeration cycles’ capability enhances. Hence, the current study is motivated to assess the feasibility of thermal energy utilization of geothermal energy for an innovative trigeneration system encompassing a bi-evaporator-based refrigerator, a heating terminal, an electricity generation setup. In this paper, a tri-generation system of cooling, heating, and power generation is proposed, which can simultaneously produce all three outputs. The Rankine cycle is combined with an improved ejector refrigeration cycle, where the outlet flow from the second evaporator creates suction in the ejector and activates the ejector refrigeration cycle. In addition, binary working fluids are used instead of pure working fluids to enhance the system's performance. The proposed system is thermodynamically analyzed based on the first and second laws of thermodynamics for various mixtures. The highest power, refrigeration capacity, and heating output are found to be 33 kW, 214 kW, and 306 kW, respectively, for the R236fa/Pentane mixture. Additionally, the highest energy and exergy efficiencies are 54.7% and 27.48%, respectively, for the R142b/Pentane mixture.

Introduction
Refrigeration cycles with extensive uses in various applications such as industrial and domestic sectors and preserving agricultural products, food, and pharmaceutical products are the most attractive option to comfort human life in different dimensions. This challenge motivates researchers to conduct more studies on developing newly devised refrigeration cycles, employing such systems within tri-generation setups, and analyzing their capabilities. Meanwhile, establishing renewable energy-based tri-generation plans to meet energy demand, particularly cooling, can have a great influence on the future of the energy conversion field, covering the rapid growth in energy consumption throughout the world.
Regarding the advantage of bi-evaporator technologies, there seems to be a potential for utilizing bi-evaporator technologies with tri-generation systems via geothermal energy as an instigator. Hence, this survey suggests a novel geothermal-powered tri-generation plant w with a modified Combined Cooling, Heating, and Power (CCHP) generation setup. Following is a list of this survey's most important novelties and works.:
• The proposal of a novel geothermal-based tri-generation plant embracing a newly devised compression/ejection cooling production cycle framework utilizing zeotropic mixtures.
• The modification of previous bi-evaporator refrigeration cycles using an ejector, regenerator, and coherent management of components to reduce wasted energy and boost the whole setup's proficiency.
• The use of energy and exergy methods to access the devised system thermodynamically.
• Conducting a sensitivity study to better understand the impact of design parameters on the performance parameters of the system.