Optimal Coefficient Of Performance Research Articles

Optimization of Triple Effect Vapour Absorption Refrigeration System: A Statistical Approach

Abstract The present manuscript optimized the First and Second Law performance of the triple effect vapour absorption refrigeration systems (TE-VARS) using statistical techniques like Taguchi, Taguchi-based GRA, and RSM-based GRA methods, which provide the most accurate and optimized results. Liquified pertrolium gas (LPG) and Compressed natural gas (CNG) are considered as the source of energy to operate TE-VARS, as the system requires significantly higher generator temperature. Also, volume flow rate of these gases along with the annual operating cost to drive the system have been presented. A thermodynamic model was first formulated using EES software for the computation of the coefficient of performance (COP) and exergetic efficiency (ECOP). The most influential parameters like temperature in the main generator, concentration and pressure at different components are studied and determined using ANOVA and Taguchi methods. The optimum parameters were determined based on the mean effect plot of S/N ratios for COP and ECOP. It has been found that the maximum COP and ECOP were calculated to be 1.915 and 0.15, respectively under the Taguchi method. Furthermore, Taguchi-GRA was used for the simultaneous optimization of the operating parameters and performance of the system. It is observed that the absorber temperature is the most influential parameter for affecting COP and ECOP. Moreover, a RSM-based GRA method was also applied and developed regression models that yield most optimum COP and ECOP as 1.963 and 0.1606, respectively. Comparison shows that the RSM-based GRA method provide the most optimum conditions, which is one of the key finding of the present study. Also, rate of exergy destruction at each component of TE-VARS has been plotted under optimized operating conditions. The optimum volume flow rate for LPG and CNG comes out to be 0.057 and 0.177 m3/s, while the minimum operating cost (yearly) are 299.827$ and 183.293$, respectively.

Solar adsorption cooling system operating by activated–carbon–ethanol bed

One efficient way to convert small thermally energized into effective cooling is through adsorption cooling technology, which increases energy efficiency and reduces environmental pollution. This study's primary goal is to hypothetically examine the thermal coefficient of performing the solar adsorptive refrigerator machine operated with an activating carbon/Ethanol operating dual. The impact of different operating situations and design factors on the machine's performance is inspected and evaluated. The present double-bed solar energy adsorptive-cooler unit is modeled by thermodynamic methodology. Then, it was analyzed to evaluate its effectiveness work under Baghdad climate conditions. For the current study, the two-bed solar adsorption cooling unit with 0.5 kW capacity input heat 11893 that operates at 5 °C for the evaporator and 45 °C for the condenser is presented. The Engineering-Equation-Solver (EES) simulation program was created and used to solve the modeling equations that predict the optimal cycle performance and evaluate the optimum reasonable values of the operation parameters of the proposed system. The pressure range for the refrigeration cycle is 2.408 kPa for the evaporation state and 23.14 kPa for the condensation state. The findings demonstrate that an optimum coefficient of performance (COP) is 0.702 at 95 °C, a 20% performance increase, which generates 39.4 of cooling water. It produced 1 kg of chilled water for 2.463 kg of activated carbon at a temperature of 5°C. The improved solar-powered adsorption systems and refrigeration technologies are appealing substitutes that can satisfy energy demands in addition to meeting needs for cooling, ice production, air conditioning, and refrigeration preservation and safeguarding of the environment with Iraq's climate conditions.

Effect of the refrigerant charge on transcritical CO2 direct evaporation ice-making system

The low global warming potential and zero ozone depletion potential of CO2 make it highly suitable for application in ice rinks. The refrigerant charge prediction model of the transcritical CO2 direct evaporation ice-making system is proposed and compared. According to the predictive results, the performance of the ice-making system was experimentally studied at three predictive refrigerant charges. The results show that the ice-making system with the refrigerant charge predicted by the comprehensive model with GC + ECH (gas cooler refrigerant charge model and evaporator refrigerant charge model with Hughmark correlations) presents the optimum performance. The refrigerant charge in the pipeline accounts for 46.6 %–57.2 % of the total refrigerant charge, so proper pipeline arrangements are crucial to reduce the overall refrigerant charge, especially before and after the throttle valve. The experiment data shows that the optimal high-side pressure of the ice-making system is between 7.9 MPa and 8.3 MPa, and the optimal COP (coefficient of performance) is between 1.34 and 1.75. Excessive or insufficient refrigerant charge leads to overall superheating or overall unsaturation of the refrigerant at the outlet of the evaporator. At the proposed refrigerant charge, both cooling capacity and COP increase by 8.3 %–38.3 % and 21.5 %–30.6 % respectively compared to other charges tested. In addition, the ice-making time at the proposed refrigerant charge can be saved by 10.0 %–15.6 %.

Exploring the Design of Solar and Foamed Based Temperature Maintenance System for Cooler

Refrigerators are an important household item that comes under the category of cooling appliances. The primary structure of the refrigerator consists of a thermally insulated compartment which provides a mechanism that lowers the temperature inside it and transfers the heat from the inside to the external environment. As it keeps the temperature low as per user requirement, it is used to preserve the food items that can be spoiled at ambient temperature. Refrigerators in available in many sizes on the market but they have some limitations for indoor usage only as they require electricity and are in large amounts. However, when people are more moving towards outdoor activities, they need to have a refrigerator to keep the necessary items which will prevent spoilage and wastage. So, this paperwork has designed a mini refrigerator that is powered by batteries and is portable which can be easily used outdoors as well. This paper deals with the working of small-size refrigerators. Thermoelectric Cooler Design is to be used as an aid in the design of thermoelectric cooler devices. This work is used to quickly model and compare alternative designs. An optimum coefficient of performance and heat pumping can be quickly determined. Other major features include the ability to change the material properties and dimensions of couples.

Three-heat-reservoir thermal Brownian heat pump and its performance limits

Three-heat-reservoir (THR) heat pump has the originality of using low-grade heat to achieve pumping heat, and it can recycle waste heat and reduce environmental pollution effectively. Based on the research ideas of macro THR heat pumps and micro three-terminal thermoelectric devices, this paper proposes a THR thermal Brownian heat pump cycle model. This cycle is driven by low-grade “heat” to work, and it may be seen as a combined cycle consisting of a two-reservoir thermal Brownian heat pump and a two-reservoir thermal Brownian engine. Using non-equilibrium thermodynamics, expressions for heating load and coefficient of performance (COP) are derived. The coupling relation between external forces of two motors is obtained by solving the heat balance equations, and cycle performance is further obtained. The maximal heating load is obtained by optimizing barrier height, and the lower limit of COP is also given. Results show that the THR thermal Brownian heat pump can achieve pumping heat by using low-grade “heat”. The internal parameters affect the coupling between two-heat-reservoir thermal Brownian engine and two-heat-reservoir thermal Brownian heat pump, which determines cycle performance directly. The curve of heating load about COP presents a parabolic-like shape, and an optimal COP exists to maximize heating load.

Statistical Analysis and Optimization of a Single-Effect Vapor Absorption Refrigeration Cycle

Abstract: This study employs Response Surface Methodology (RSM) with a Box-Behnken design to optimize the Coefficient of Performance (COP) in a Single-Effect Vapor Absorption System. The thermodynamic model considers a 1-ton refrigeration (TR) system utilizing Lithium bromide-water as the refrigerant, and simulations are conducted using the Engineering Equation Solver (EES). The optimization process identifies optimal values for the generator, absorber, condenser, and evaporator temperatures, set at 90°C, 33°C, 33°C, and -5°C, respectively, resulting in an achieved optimum COP of 0.716. Statistical analysis through ANOVA of the quadratic regression model reveals a significant F-value of 110.62, with a low probability value (p=0.0003), attesting to the model's robustness. Key statistical metrics for the model encompass a standard deviation (Std. Dev.) of 0.0059, a mean of 0.8956, a coefficient of variation (C.V. %) of 0.6559, an R² of 0.9901, an adjusted R² of 0.9811, a predicted R² of 0.9159, and an adequate precision of 38.2967. This research offers crucial insights into enhancing the performance of a Single-Effect Vapor Absorption System, thereby contributing to the advancement of energy-efficient refrigeration technologies

Techno-economic assessment of solar-driven ejector refrigeration system assisted with daytime radiative condenser

Solar-driven ejector refrigeration is an emerging technology, but not sustainable due to huge heat rejection to the environment, leading to the heat island effect. However, this can be made sustainable by utilizing a daytime radiative condenser, but not yet been explored. Hence, a novel solar-driven ejector refrigeration system assisted with a daytime radiative condenser is investigated based on energy, exergy and economic perspectives. This system is powered by a parabolic trough collector along with thermal energy storage and double two-phase ejectors. The system performance is optimized by employing the genetic algorithm. The impact of several operating scenarios and seasonal climatic conditions is explored for different refrigerants. The best optimum coefficient of performance and exergy efficiency are obtained with the R123, but the total cost and radiative condenser area are lowest with the R1234ze(E). The performance is higher with lower ambient and radiative condenser temperatures but with higher solar irradiation for all three refrigerants. The performance is maximum during December for Jaisalmer and January for Varanasi and Kolkata, while lowest in May for Jaisalmer and June for Varanasi and Kolkata. The specific total cost and radiative condenser area are maximum from July to August for all considered locations. This study reveals the proposed system as a promising option, but the large space requirement may be the main hurdle behind the practical implementation.

Analysis and optimization of injection characteristics and comprehensive performance of low GWP refrigerant HP-1 in high temperature heat pump systems

In the context of low-GWP refrigerants becoming a research hotspot, the environmentally friendly refrigerant HP-1 with independent intellectual property rights in China has demonstrated significant advantages in fields such as data centers and 5G base stations. However, there are few applied studies in the field of high-temperature heat pumps (HTHPs), therefore, in this study, HP-1 was utilized in HTHP system and this process was combined with the injection technology. It has been proven to be an effective approach for performance improvement. The injection characteristics of HP-1-based HTHP were analyzed and optimized with a focus on safety, stability, and efficient operation. The application advantages of HP-1 were compared and analyzed in terms of thermodynamic performance and Total Equivalent Warming Impact. The results indicated that there were three types of characteristic injection pressures based on system performance, corresponding to the maximum coefficient of performance (COP), the lowest electronic expansion valve inlet refrigerant temperature, and the lowest exhaust temperature of the compressor. Further, the corresponding control equations for injection pressure were obtained. Based on the safety injection pressure, the optimal COP under injection pressure could effectively improve the COP of the system by 2.1–5.2 %, and the exhaust temperature also increased by 6.1–10.1 %. When the temperature of the heat source was 50 °C and the target heating temperature was 120 °C, the heating capacity of HP-1 increased by 10.8 % compared with that of R245fa, the COP of the system increased by 2.7 %, and the volume heating capacity increased by 10.3 %. Moreover, the emission reduction effect of HP-1 was significant, and the carbon dioxide emissions were reduced by 15.4–39.1 %. The analysis shows that HP-1 exhibits better performance and environmental characteristics than HFC-245fa. This study is of guiding significance to improve the thermodynamic performance of HTHP, for the safe and efficient operation and energy saving and emission reduction in the industrial field.

Experimental performance analysis of evacuated tube type direct-expansion solar-assisted heat pump system

ABSTRACT The direct-expansion solar-assisted heat pump (DX-SAHP) have proven to be one of the strategies in reducing energy consuming for domestic hot water supply. The poor pressure resistance of the collector, high heat loss from radiation for the traditional bare-plate type DX-SAHP limits its popularization and application. To solve this problem, a DX-SAHP system using evacuated tube type collector-evaporator was proposed in this post. System optimization can not only reduce operating costs, but also results in energy savings. Thus, a DX-SAHP prototype was established and tested under various running conditions to obtain the optimal running parameters. Based on experimental data, the impacts of refrigerant charge, solar radiation intensity, and ambient temperature on the performances of evacuated tube type DX-SAHP system are investigated and evaluated. The outcome indicates that this system coefficient of performance (COP) increases by 73.4% with the decrease of charge amount of refrigerant in the range of 5.66–6.67 kg. And, the average collector efficiency is 0.71 with a refrigerant charge of 5.66 kg. And, the optimal COP of this presented system is 5.27 when an ambient temperature, solar radiation intensity, and refrigerant charge are 26.3°C, 954.37 , and 5.56 kg, respectively.

Multi-objective optimization of fractal-tree microchannels in a rectangular heat sink by a distributed-adaptive genetic algorithm

Recently, an innovative heat dissipation technique of fractal-tree structures has attracted attention due to its excellent high heat transfer efficiency and low pumping power. Though the impact of geometrical parameters such as branching level and dimension ratios of successive branches on the heat transfer efficiency and pumping power are considered to be critical, the impact mechanisms are still not well studied and formulated. Hence, there is still no clear method to optimally arrange the fractal-tree microchannels (FTMCs) in a rectangular heat sink to achieve better thermal and hydraulic performance. Therefore, we developed a multi-objective optimization algorithm (distributed-adaptive genetic algorithm, DAGA) to optimize the different types of novel FTMCs concerning achieving an optimal COP (coefficient of performance, heat transfer/ pumping power). The developed DAGA can improve the computational efficiency and the quality of optimum by around 87.63% and 12.48%, respectively in the present work. Then, taking conventional rectangular parallel microchannels (RPMCs) as a reference, the COP of the optimized FTMCs in the same heat sink shows an enhancement of around 0.09 ∼ 0.57. The highest COP is achieved by the three-level branching FTMC. Furthermore, the optimized results reveal that branching level, bifurcation number, and microchannel width at the first branching level are sensible, while dimension ratio factors and microchannel length at the first branching level show low sensibility to the COP of FTMCs.

Analysis of the Coefficient of Performance (COP) on the Car’s Air Cooling System Using a Training Kit with Constant Rotation

The performance of the air condition system is strongly influenced by the compressor work, the condenser cooling temperature. So that the compressor working pressure (suction) and condenser cooling play a very important role in the performance of the air conditioning system which will have an impact on compressor work, compressor power, refrigeration impact, isentropic efficiency and coefficient of performance (COP) of the car air conditioning system. From the research, data will be obtained which include the pressure value on the refrigerant, namely P1 and P2, the temperature on the refrigerant, namely T1, T2, T3 and Tcabin, at the point of installation of the Manifold Gauge and Thermocouple. The research data is then processed and analyzed to obtain performance at constant rotation with variations in compressor working time both actual and theoretical as well as the efficiency of the ac system. From the results of the study, it was found that the compressor rotation was 2300 rpm with a constant rotation then measured the pressure and temperature of the refrigerant, then temperature data was obtained and analyzed to obtain the enthalpy value, thus obtaining the coefficient of performance (COP) of the car air conditioning system. The coefficient of performance (COP) of the resulting system is greater than the actual COP, the optimal COP occurs at P1 30 psi and P2 340 psi working pressures, the actual COP is 3.4848 and the theoretical COP is 4.1500, with an efficiency of 83.97% at 360 seconds.

A novel variable speed ASHP frosting suppression operation method based on the frosting suppression performance map

For variable speed (VS) space heating air source heat pump (ASHP) unit, its different operation speed combinations may significantly affect the frosting suppression and heating performances. However, currently there is no frosting suppression operation method for VS ASHP units, so that their frosting suppression ability using different speed combinations is not fully utilized. Therefore, a novel frosting suppression operation method based on the frosting suppression performance map for VS ASHPs has been proposed, and its development through experimental is reported in this paper. Firstly, a novel operation method to guide the frosting suppression operation for VS ASHPs is proposed. Secondly, an experimental setup with two VS experimental ASHP units, test conditions, and nine study cases are described. Thirdly, the speed combinations that led to different frosting suppression potentials but with the same output heating capacity were determined using the developed frosting suppression performance map, and comparative tests were carried out. It is shown that the use of the proposed novel frosting suppression operation method with the optimal coefficient of performance (COP), which can increase the total output heating capacity (Q) by 15% and the COP by 25%. The proposed novel operation method was straightforward and simple to implement, which could contribute to the further development of frosting suppression operation for ASHPs.

Novel configuration of dual-temperature condensation and dual-temperature evaporation high-temperature heat pump system: Carbon footprint, energy consumption, and financial assessment

To achieve the goal of carbon neutrality for the application of industrial heating by recovery waste heat, the concept of dual-temperature condensation and dual-temperature evaporation is proposed for the high-temperature heat pump (HTHP) by introducing the techniques of ejector and two-stage compression. The energy, exergy, emission, and economic models are developed and optimized for the two new proposed systems. Then, the energy consumption, CO2 emissions and cost (LCC) during the whole life cycle are compared with five existing heat pumps and four traditional boilers. The highest coefficient of performance (COP) of heat pump (HP) can be got when intermediate water temperature on the heat sink side is optimum. The new proposed systems have better performances than the other five HTHPs. During the rated working condition, discharge temperature decreases by the use of dual-temperature condensation and dual-temperature evaporation HP with an ejector (Ej-DCDE). The optimal COP of Ej-DCDE-2 is 4.25, which is 11.55% and 1.43% higher than dual-temperature condensation and single-temperature evaporation HP and Ej-DCDE-1, respectively. The exergy destruction of Ej-DCDE-2 is reduced by 27.88% compared with basic heat pump (Base). Moreover, Ej-DCDE-2 has the lowest primary energy consumption of 14.62 ktoe, 22.19% and 25.09% lower than Base and oil-fired boiler during the total working period, respectively. In general, HTHPs have lower carbon dioxide, gaseous and particular pollutant emissions compared with boilers, especially Ej-DCDE-2. Finally, Ej-DCDE-2 has the minimum LCC, which is 14.67% and 11.75% less than Base and coal-fired boiler. Ej-DCDE-2 shows the most potential advantages of all the heating solutions and is recommended to replace traditional boilers for industrial heating.

Performance analysis and optimisation of the chiller-air handling units system with a wide range of ambient temperature

The integrated optimisation modelling for the chiller-air handling units system is developed for increasing the efficiency and energy utilisation of system. A building management system in the chillers network controls the cooling load to ensure the specified desired set temperature of the cooling air within the building can be satisfied. Unfortunately, the desired set point temperature of the cooling air is a fixed value and does not vary with the dynamic change of cooling demand with different ambient temperatures. Therefore, the power consumption of the chillers and the building cooling requirement with a wide range of different ambient temperatures is properly modelled by optimising the performance of chillers, air handling units, cooling towers, and water pumps. The linear programming model for the system is established to model a real representation of the chiller-air handling unit system. The result shows that the optimal coefficient of performance is greater by about 7%–10% than the current chiller system. The optimal power consumption of the chiller system reduces to 3%. Overall, the optimal decision solutions could be used as the potential improvement strategy to control the desired set point values in the building management system for efficient chiller-AHU system.

Thermoeconomic Analysis of Novel Vapor Compression-Absorption Multi-Target-Temperature Cascade Refrigeration System

Abstract To fulfill the requirement of multi-refrigeration temperature, multi-target-temperature techniques are increasing research interests for industrial and commercial applications. Taking forward the previous research keeping in mind the electric power saving, a novel vapor compression-absorption multi-target-temperature cascade (VCAMTTS) system is proposed, in which NH3-H2O pair is used as vapor absorption section in the high-temperature circuit whereas two out of three refrigerant R717, R410A, and R134a are used in two lower circuits results in three possible configurations as NH3-H2O/R717 + R410A, NH3-H2O/R410A + R134a, and NH3-H2O/R134a + R717. This detailed analysis is based on the selection of the best configuration, investigating these on every aspect of energy, exergy, and economy (EEE). The whole investigation revolves around the parameters such as coefficient of performance (COP), exergy efficiency, and their sensitivity due to change of evaporator temperature and refrigerating capacity distribution ratio, exergy-economic factor, and product cost rate. Based on its best thermodynamic and thermal-economic performance, NH3-H2O/R410A + R134a (NHRARa) system can be a better option for multi-target-temperature refrigeration applications. Further, from the thermoeconomic analysis the optimum COP, exergy efficiency, and minimum cost obtained are about 0.3378, 8.29%, and 24.19 $/h, respectively.

High-performance polymer-based regenerative elastocaloric cooler

Alternative methods of refrigeration are critical for performance optimization and environ- mental sustainability. Prototype systems using caloric materials have shown the advantages of a high coefficient of performance (COP) and low global warming potential. Elastocaloric elastomers can meet ongoing needs, but their implementation in functional heat pumps or coolers remains challenging due to their requirement for a large deformation and low thermal conductivity. Moreover, a scalable design is required to achieve high cooling power. As a leap forward for the use of polymers in larger scale caloric devices, we developed experimental elastocaloric polymer coolers with two different geometries using natural rubber tubes. We confirmed that a suitable geometry partially compensated for the low thermal conductivity and led to performances comparable to those of other caloric devices. Several operating conditions were tested to determine the optimal temperature span, cooling power, and COP for both device geometries. Under a specific operating condition, one of the prototypes exhibited a maximum temperature span > 8 K, a maximum COP of 6, and an output cooling power of 1.5 W; this power outperforms other prototypes based on polymers or ceramics. The parallelization of rubber tubes will facilitate realistic elastocaloric polymer coolers on a larger scale.

Experimental studies on absorption-compression hybrid refrigeration system using 1,1,1,2-tetrafluoroethane/tetraethylene glycol dimethyl ether as working pair

The feasibility of combining novel halogenated hydrocarbon-based working pairs with low-pressure compression-assisted absorption refrigeration system (LCARS) was proved for the first time from the experimental perspective. An experimental prototype of the absorption-compression hybrid refrigeration system with a 1 kW cooling capacity was designed and tested to explore actual performances of selected R134a-DMETEG and performance improvements from compression in LCARS. At an evaporation temperature of approximately 5 °C, as the hot water inlet temperature and the solution flow rate change from 75 to 95 °C and 1.2–2.7 L/min, respectively, the coefficient of performance (COP) in the single-stage absorption refrigeration system (SSARS) varies from 0.211 to 0.412. At an increased evaporation temperature of approximately 10 °C, as the hot water inlet temperature and flow rate increase from 70 to 80 °C and 1.18–2.89 L/min, respectively, the COP in the SSARS varies from 0.238 to 0.552, while the COP in LCARS is improved and varies from 0.470 to 0.617. The LCARS increases the COP by a maximum of 91.04 % and can utilize a lower-grade heat source more efficiently due to its higher optimal COP at reduced hot water inlet temperatures. This study provided one feasible technical approach of combined use of R134a-DMETEG and LCARS to make up for the application limitations of traditional working pairs, contributing to application promotions of absorption systems, especially for the occasions with high requirement on safety and lightweight.

Analysis of a New Super High Temperature Hybrid Absorption-Compression Heat Pump Cycle

Utilization of high-temperature energy in industrial production processes is often exhausted by huge low-temperature waste heat without recovery. Thus, energy efficiency is quite limited. Heat pumps are widely used as a high-efficiency waste heat recovery system and are divided into vapor compression cycle, driven by electricity, and absorption type, driven by steam or hot water. However, compression heat pumps are quite difficult to reach more than 100 °C due to the temperature and compression limits of compressors and the working medium. Meanwhile, the COP (coefficient of performance) of an absorption heat pump is quite low due to the thermodynamic cycle characteristics. In order to increase the outlet temperature and COP significantly, a new type of compression-absorption hybrid heat pump cycle is presented and simulated. Compared with traditional cycles, this heat pump can reach the heat sink temperature of 200 °C with a highly satisfactory COP. This heat pump could reach the optimal COP of 3.249 when the pressure ratio of the compressor is 6.5, the coupling temperature of the low-pressure stage is 55 °C and the coupling temperature of the high-pressure stage is 73 °C. Exergy analysis shows that evaporators and condensers show better efficiency. This heat pump could be promising in different kinds of heat recovery.

Energy, exergy, economic and environmental analyses and optimization of a novel vapor injection autocascade heat pump for high-temperature water heating

Aiming to develop a high-efficiency and low-cost high-temperature heat pump with large temperature lift ability, a novel vapor injection autocascade heat pump for high-temperature water heating is proposed in this paper. The proposed system utilizes the vapor injection technique to improve the limited performance of the conventional autocascade system and can achieve outstanding heating performance with over 100 °C heating temperature. The energy, exergy, economic and environmental performance of the proposed system are investigated by simulation method and compared with those of the conventional autocascade heat pump. The proposed system averagely improves the heating coefficient of performance and capacity by 51.8% and 104.3% over the conventional system when the evaporating temperature ranges from 0 °C to 20 °C, respectively. The exergy analysis indicates that the excellent exergy performance of the proposed system mainly benefits from the irreversible loss reductions in the throttling valves and cascade condensers. The proposed system possesses the lowest energy cost except for the coal-fired boiler, and produces the minimum pollutant emission except for the gas-fired boiler. The heating coefficient of performance of the proposed system is improved by 12.4% ∼ 14.0% through single-objective optimization. The optimal coefficient of performance and levelized cost of energy are 2.59 and 0.070 $ kWh−1, respectively.

Analysis of the Air-Reversed Brayton Heat Pump with Different Layouts of Turbochargers for Space Heating

The air-reversed Brayton cycle produces charming, environmentally friendly effects by using air as its refrigerant and has potential energy efficiency in applications related to space heating and building heating. However, there exist several types of cycle that need to be discussed. In this paper, six types of air-reversed Brayton heat pump with a turbocharger, applicable under different heating conditions, are developed. The expressions of the heating coefficient of performance (COP) and the corresponding turbine pressure ratio are derived based on thermodynamic analysis. By using these expressions, the effects of turbine pressure ratio on the COP under different working conditions are theoretically analyzed, and the optimal COPs of different cycles under specific working conditions are determined. It is observed that Cycles A and C have the highest heating COPs, and there is an optimal pressure ratio for each cycle. The corresponding pressure ratio of the optimal COP is different, concentrated in the range of 1.5–1.9. When the pressure ratio reaches the optimal value, increasing the pressure ratio does not significantly improve the heating COP. Take Cycle F as an example: the maximum error between the calculated results and experimental observation is lower than 5.6%. These results will enable further study of the air-reversed Brayton heat pump with a turbocharger from a different perspective.