Conventional Heat Pump System Research Articles

Performance evaluation of underground thermal storage integrated dual-source heat pump systems

The increasing demand for electricity stresses the existing electric grids. Buildings consume 73% of all U.S. electricity and are responsible for 30% of U.S. greenhouse gas emissions. Integrating thermal energy storage (TES) in building heating/cooling systems, which consume considerable electricity, can mitigate the challenges to electric grids. This study reports on a novel thermal energy storage device integrated heat pump system to reshape the building electricity demand profile while maintaining thermal comfort. The annual performance of the proposed system has been evaluated through a dynamic system simulation with high fidelity in the Modelica platform. The dynamic model of the novel hybrid component named ‘dual purpose underground thermal battery’ was developed and validated. It was then incorporated into the system model. Given a time-of-use tariff, a rule-based control strategy was designed to shift the electric demand and switch the heat pump source for a typical single-family house in different climate zones of the United States. The system performance of the new TES-integrated dual-source heat pump was compared with that of a conventional air-source heat pump system. The results indicate that the proposed system can reduce the annual HVAC electricity cost by up to 52% while saving 45.2% on electricity consumption. In the Northern areas, the annual peak load of the HVAC system can be reduced by 64.9%. However, this reduction is less in the Southern areas as the system’s higher efficiency in winter dominates the overall energy-saving potential.

Study on a high-performance heat-driven thermoacoustic heat pump

Heat-driven thermoacoustic heat pump (HDTAHP) is a promising heating technology with high reliability. Current HDTAHP face the challenge of being relatively inefficient and not capable of further improvement. This study aims to address this problem by introducing an innovative energy matching tube (EMT) into the conventional thermoacoustic heat pump to realize more reasonable acoustic power matching between the engine and heat pump units, further greatly improve the system efficiency. The key reason for the limited performance of HDTAHP is first explored and lies in the constraints that exist between temperatures. Through Sage modeling and calculations, the comparison between the proposed system and the conventional thermoacoustic heat pump system verifies that the introduced EMT can dramatically increase the system performance. At a heating temperature of 700 K, the overall Coefficient of Performance (COPh) of the system is improved by 43.7 % compared to the conventional thermoacoustic heat pump without EMT. The performance under different working temperatures is then investigated and demonstrated a strong adaptability of the proposed system under different heating temperature objectives. The comparison with existing thermoacoustic-Stirling heat pumps further indicate the high-performance improvement by EMT and promising potential of thermoacoustic heat pumps in domestic heating domain.

Fully electrified heat pump assisted distillation process by flash vapour circulation

In industrial processes there are instances where heat pump assisted distillation falls short of full electrification, necessitating an auxiliary reboiler. To solve this limiting issue, this short communication proposes a new method using flash vapour circulation (FVC) to recuperate the waste heat within the heat pump cycle. This method incorporates a flash drum after the throttling valve to generate flash vapour. Rather than employing an auxiliary cooler for condensing the mixed vapour-liquid in a conventional heat pump system, the produced flash vapour is circulated back to the compressor inlet to enhance the recycled heat in the reboiler. With proper energy match, this approach has the potential to realise full electrification of distillation. The distillation of methanol/water serves as an illustrative case study, showcasing the viability of FVC which allows additional 22% energy savings, as compared to mechanical vapour recompression. Yet, this strategy may not be advantageous if the waste heat is already maximally utilised in preheating both the compressor and column inlet feed. The separation of tetrahydrofuran/water is used as case study to demonstrate the limitations of this approach.

Assessment of Environmental Impacts of Thermal Caisson Geothermal Systems

This paper investigates the total environmental impacts of a thermal caisson (TC) system by implementing a life cycle assessment methodology. The total environmental impacts consider the comprehensive effect on the environment across two life cycle stages: manufacturing and operation. A comparison between the TC results and two different HVAC systems, including air-conditioning/furnace and conventional ground-source heat pump (GSHP) systems, was made by adopting the ReCiPe 2016 methodology. This study reveals that the operation phase is the predominant contributor to environmental impacts across systems, mainly due to its extended duration. Specifically, the operational impacts of GSHPs are substantial, accounting for approximately 87% of total environmental impacts. A TC GSHP system demonstrates a notable environmental advantage, achieving a 79% reduction in total environmental impact when compared to traditional AC/furnace systems. This represents a 21% improvement over conventional GSHP systems. Despite this substantial reduction in total environmental impact, the TC GSHP system shows an almost 5% increase in the resource availability damage category relative to the conventional GSHP, which is attributed to its higher material consumption. These results highlight the TC GSHP system’s superior efficiency in reducing environmental impacts and its potential as a more sustainable alternative in residential heating and cooling applications.

Thermodynamic and economic analyses of modified ejector enhanced solar-air composite dual-source heat pump system in residential buildings

This research utilizes an ejector enhanced solar-air composite dual-source heat pump (EDHP) system for water heating in residential buildings. The main advantage of the EDHP system is the use of an ejector and dual-heat source to efficiently utilize solar energy, thereby enhancing heating performance. This ejector operates by utilizing a refrigerant stream from the solar collector line with higher pressure to elevate the suction pressure of the compressor. This feature enables the EDHP system to maintain stable heating performance even in adverse weather scenarios with low temperatures or limited solar radiation. Thermodynamic modeling using energetic and exergetic analysis methods is employed to theoretically evaluate the conventional air-source heat pump and EDHP systems. The energy analysis of the EDHP system using R134a refrigerant has shown significant improvements in both heating coefficient of performance (COP) and exergy performance (ECOP). Under specific conditions, such as an ambient temperature of −5 °C and an irradiance level of 250 W∙m2, and utilizing a 20 m2 PVT (Photovoltaic and Thermal) collector for a heating supply of 5 kW, the EDHP system exhibits a 23.64 % increase in COP and a 25.83 % increase in ECOP. Furthermore, when the electricity generated by the PV system is incorporated into the EDHP system, the demand for electricity from the grid can be reduced by up to 51.96 % under the same conditions. In the Beijing area and considering the current energy price system, the heating operating cost of the EDHP system is 0.206 Yuan/kWh. Compared to a standard air-source heat pump system, the payback period for EDHP system ranges approximately from 10 to 12 years, taking into account an annual heating period of 5 months. Among the alternative refrigerants to R134a in the EDHP system, R152a is found to be the most suitable. It shows COP improvements of 24.92 %–30.0 % and ECOP improvements of 24.89 %–29.96 %. This innovative approach opens up new possibilities for the application of heat pump technology under adverse weather conditions in residential and commercial buildings.

Economic and performance analysis of ground source heat pump system for high-rise residential buildings considering practical applications

Ground source heat pump (GSHP) systems are being applied in various buildings to achieve carbon neutrality and zero energy building. Large-scale residential buildings have seen limited use of GSHP systems due to the absence of design guidelines and established operation methods. While design guides for general buildings are available from associations or institutes, there is a scarcity of designs and operation guides that consider dynamic simulations with occupant conditions and detailed load conditions. Generally, it is crucial for the economic analysis to optimally design suitable system capacity and accurately predict the performance. Therefore, in this study, the dynamic energy simulation model was constructed by considering the condition of the occupants and system operation and quantitively analyzed economic feasibility and system performance. Furthermore, the sensitive analysis based on the practical range of operation was conducted for comparison with conventional systems, district heating (DH) and electric heat pump (EHP) system. The heat pump's performance improved by up to 12.6% based on GSHP system design factors. Although the initial investment cost of the GSHP system was 51.5–84.7% higher than DH and EHP systems, its annual operating cost was 20.8–33.1% lower. The ground source heat exchanger had the most significant impact on performance, while the thermal storage tank's capacity had the largest impact on annual operating costs, aligning with previous research findings. In terms of carbon emissions, the annual CO2 emissions of the GSHP system were 49.1% lower than those of the existing system. The study highlights that GSHP systems can achieve high performance, economic efficiency, and low CO2 emissions based on the design approach. Additionally, the study provides valuable insights into GSHP system design, offers quantitative feasibility data, and compares them to traditional heating and cooling systems, taking practical cost considerations into account.

Photovoltaic Thermal Technology Collectors, Systems, and Applications

Photovoltaic thermal (PVT) technology has been drawing attention recently. Electrification of the heating sector with heat pumps run by carbon‐free electricity sources like photovoltaics is setting the ground for the interest. This article gives insight into PVT technologies and collector designs according to application and operating temperatures. For most conventional designs, examples like prototypes from Research & Development projects are presented. In addition, commercial products are listed along these categories, and the influence on the gross thermal and electrical yield is depicted based on Solar Keymark certification data. The process of certification is presented in a comprehensive way, showing current limitations, giving an outlook on the most recent approach for enhanced procedures and specifications. Finally, different system layouts are presented, and examples from installations combined with a heat pump are given with their specific performances. Real performance data of several PVT installations are compared to conventional heat pump systems. The identified seasonal performance factors are in a range from 3.4 to 4.2 and in between air source and ground source heat pumps. Continuous monitoring and derived data are enablers to discover the decisive influence of the system layout and dimensioning on performance indicators like, for example, operating temperatures over the year.

Prospective study of a novel heat pump system with solar energy spectral beam splitting

Renewable solar energy as a resource for carbon emissions reduction, its application and promotion are hindered by low energy utilization efficiency. Photovoltaic modules mainly convert solar energy into electricity only in the high-frequency spectrum band. In order to achieve a high coefficient of performance, a novel heat pump system with solar energy spectral beam splitting was developed by matching the energy grade and heat pump cycle operating conditions. This also addresses the issue that the conventional heat pump system cannot supply heat efficiently and stably in the cold region of North China. Theoretical investigations were carried out on the distribution of parameters of energy load and efficiency. Compared with conventional PV modules, solar energy utilization with spectral beam splitting, which divides solar energy into the low-frequency spectrum for thermal energy collection and the high-frequency range for power generation, ensures high power production efficiency and utilization efficiency by the cascade thermal and electric energy exploitation in the proposed novel heat pump system. Partial thermal energy is used to provide the hot water, and the rest is upgraded by an ejector-based heat pump system to meet the space heating requirements. Therefore, the novel heat pump system achieves the combined supply of space heating, hot water, and electricity with high solar energy utilization efficiency through active energy conversion and thermal energy recovery. The goal of creating a structure with zero electric power consumption appears promising. When compared to the typical single PV system's (30.7%) efficiency, the suggested system's overall energy usage efficiency (up to 81.7%) is noticeably higher. In extreme cold areas, the performance superiority of the novel system is more prominent.

Performance assessment of a two-stage evaporation grade compression heat pump system for double temperature level drinking water production

The heat pump is widely used for space and water heating, but it has problems of low heating efficiency and inadequate heating at a large temperature span. According to the concept of energy cascade utilization and production, a two-stage evaporation grade compression heat pump (TE-GCHP) system is proposed in this paper for double temperature level boiled drinking water production. In this novel system, the application of grade compression matching multistage evaporation process realizes cascade utilization of the low grade thermal energy and cascade production of the hot drinking water, i.e. the refrigerant vapor from the intermediate-temperature water-cooling evaporator is sucked into the intermediate pressure suction port of the compressor to undergo the compression process of low compression ratio, while the refrigerant vapor from the low-temperature air-cooling evaporator is sucked into the low pressure suction port of the compressor to undergo the compression process of high compression ratio, so as to improve heating performance of the TE-GCHP system at large temperature spans. The energetic and exergetic analysis methods are used to evaluate heating performance of the proposed system and comparisons with the conventional waste heat-recovery single-stage compression heat pump (WH-SCHP) system are also discussed. The results indicate that there are the optimum water inlet temperature of medium-temperature water chamber and the optimum first-stage compression ratio to obtain the highest COP and exergy efficiency as well as the lowest power consumption, and energy-saving and economic performances of TE-GCHP system are markedly superior to those of WH-SCHP system and electric boiler. At evaporating temperature in the range of −10 °C to 30 °C, COP of TE-GCHP system is increased by1.06～1.29, and its exergy efficiency is improved by 2.17 %～10.62 %, while exergy loss of TE-GCHP system is reduced by 27.49 % on average, as compared to WH-SCHP system. In addition, as condensing temperature declines from 130 °C to 100 °C, power consumption of TE-GCHP system is decreased by 20.13–35.07 % compared with WH-SCHP system, whereas exergy efficiency of TE-GCHP system is on average 7.99 % higher than that of WH-SCHP system. In addition, the annual costs of the proposed system are 53.20 % and 69.68 % lower than those of the WH-SCHP system and electric boiler respectively.

Experimental Performance Analysis of Ejector Heat Pump-Water Heater Under Transient Conditions

Net-zero energy buildings are on the agenda of international community due to reducing energy consumption in the building, thus dropping carbon emissions and negative environmental effects. One of the solutions is to utilize heat pumps to decrease energy consumption in the building. In this study, the idea of ejector utilization in a heat pump system was investigated in an experimental test facility by comparison to a conventional heat pump system (without an ejector). The experimental facility, which utilizes hot and cold water as the heat source, can operate in two modes: The ejector heat pump water heater (EHP-WH) and heat pump water heater (HP-WH). The system was tested in transient conditions and the effect of ejector utilization on the system was determined. Results indicate that EHP-WH mode (COP between 5 and 6) had an average of 5.5% higher COP value than HP-WH mode (COP between 4.5 and 5.5). Furthermore, the heating capacity obtained in EHP-WH mode was 30% higher than in HP-WH. Additionally, the water cooler loop’s water temperature was 64.5% higher in EHP-WH mode than in HP-WH. Finally, it is determined that the ejector positively impacts on the performance of HP-WH system.

Investigation of the integrated fuel cell, battery, and heat pump energy systems

The integration of an advanced fuel cell battery electric vehicle was proposed to extend the driving range, increase the overall energy efficiency, and produce an additional cabin space heating service for on-board vehicle application in winter. The adopted heat pump absorbs heat from the fuel cell and battery during charging and discharging scenarios at the heat pump's cold end and transfers it to the cabin supply air for cabin heating. A numerical model for the proposed system was developed and validated by published experimental results. A comprehensive evaluation of the influence of fuel cell output current, battery discharging rate, ambient air temperature, evaporator coolant inlet temperature and refrigerant subcooling degree on the Coefficient of Performance (COP), outlet air temperature, and Equivalent Effective Battery Capacity (EEBC) were conducted. In addition, in this study, a detailed comparison of proposed system to previously published existing systems was carried out in terms of COP, heating capacity, EEBC, and operating price in order to examine the advantages of the proposed system. Results showed that the proposed system was not sensitive to ambient air temperature, but evaporator coolant inlet temperature had the greatest impact on COP, compared to other defined independent variables. A maximum COP of 6.07 could be observed when the evaporator coolant inlet temperature was 32 °C. Although increasing fuel cell output current and battery discharging rate could increase heating capacity, it would decrease outlet air temperature as well. The price of a single charging cycle for running for a 4-hour period was estimated. Compared to conventional Electric Vehicle Air Source Heat Pump (EVASHP) system and Positive Temperature Coefficient (PTC) heaters, the proposed system has the lowest cost which was £10.40per charging cycle while the others are £13.8 and £19.2 respectively when providing the same EEBC and heating capacity. Additionally, the payback period was 10,500 charging cycles. Overall, this study provides a potential solution for efficient cabin heating of electric vehicles in extremely cold weather with twice the EEBC of the existing EVASHP system and with 2.8 times of a PTC system both at −20 °C and the operating price is also 1/3 lower than the existing EVASHP. Meanwhile, the COP of the proposed system is 2.3 times that of the existing systems. It can sufficiently increase the driving range of electrical vehicles in winter and eliminate driving range anxiety.

Experimental study on energy, exergy, and exergoeconomic analyses of a novel compression/ejector transcritical CO2 heat pump system with dual heat sources

A novel compression/ejection transcritical CO2 heat pump system with dual heat sources (CHP) was proposed in our previous research. This paper experimentally investigates the feasibility and performance of the novel system and compares it with the conventional transcritical CO2 heat pump system (THP). The experimental results show that the maximum heating capacity and outlet water temperature can reach 50.49 kW and 85.8℃; The maximum exergy destruction of the novel system at 20 Hz to 30 Hz occurs in the gas cooler, which varies from 701.05 W to 1335.47 W, but the maximum exergy destruction at 35 Hz is the compressor, which is 1824.21 W; The total exergy cost rate of the throttle valve plays a dominant role in the system operation. In addition, the coefficient of performance (COP) and the exergy efficiency (ηEX) of the CHP are higher than that of the THP; The COP, ηEX, and IREX improvements of the CHP over the THP at the optimum discharge pressure, and the maximum improvements accordingly are 14.83 %, 38.14 %, 10.26 %, respectively. It can be concluded that the novel system is feasible and superior to the THP system. The research results will help to further promote the research and application of air source heat pumps integrating solar energy or geothermal energy due to the addition of the water source evaporator.

Simulation study of an open compression absorption heat pump in water and heat recovery of low-temperature and high-humidity flue gas

Realizing the recovery of latent heat and moisture from low-temperature and high-humidity flue gas (LHFG) can effectively improve energy efficiency and reduce carbon emissions. A novel open compression absorption heat pump (OCAHP) is proposed to fulfill the demand for flue gas water and heat recovery. In this paper, Aspen Plus is used to establish a model, and the coefficient of performance (COP), water and heat recovery rate are evaluated to investigate the effects of the gas inlet temperature, compression ratio, liquid-to-gas ratio, and absorber inlet solution temperature parameters on water and heat recovery performance for OCAHP. The parameters are optimized, and exergy analysis is carried out. The simulation results show that wet flue gas with successive adiabatic compression and CaCl2/H2O solution absorption has significant water and heat recovery performance. The results also prove that the water recovery efficiency of the OCAHP system is 82.4% at a compression ratio of 1.4, which is approximately 12.3% higher than that of the conventional open absorption heat pump (OAHP) system, and it is suitable for wet flue gas with a higher saturation temperature. Furthermore, exergy analysis shows that the exergy efficiency of the OCAHP system is higher than that of the conventional OAHP system, while the exergy loss is mainly concentrated in the regenerator heating process and the solution-water heat exchanger.

Performance and optimization of a novel solar-air source heat pump building energy supply system with energy storage

In order to solve the problem that the traditional heat pump system in the cold area of North China cannot supply heat efficiently and stably, a novel solar-air source heat pump system is proposed to meet the needs of building energy consumption. In winter, the latent heat of water in the ice tank is used as the main low-temperature heat source for the heat pump, and the outdoor air is used as the auxiliary heat source. During the day, the solar energy is used to restore the heat of the ice tank, so as to realize the complementary utilization of renewable energy. The air source heat pump can be used for cooling in summer. In addition, combined with night energy storage (cold storage and heat storage), the “peak load shifting” and the minimization of building operation energy consumption and cost are realized. The experimental platform and simulation model of the system are established, and the operation and design scheme of the system are optimized with the optimal economy. The optimization results show that the system can still maintain efficient operation under continuous extreme weather in winter and summer, and the SPF of the system in winter and summer are 2.93 and 2.6, respectively. Solar photovoltaic power generation meets part of the power demand of the system, which can save about 1.85 t of standard coal compared with thermal power generation. Compared with a conventional air source heat pump system, the novel system has better economy and a dynamic investment payback period of 3.86 years. The proposed system presents a way to meet building energy supply that is worthy of popularization and application in cold areas.

Exergy Efficiency and COP Improvement of a CO2 Transcritical Heat Pump System by Replacing an Expansion Valve with a Tesla Turbine

The heat pump system has been widely used in residential and commercial applications due to its attractive advantages of high energy efficiency, reliability, and environmental impact. The massive exergy loss during the isenthalpic process in the expansion valve is a major drawback of the heat pump system. Therefore, the Tesla turbine exergy analysis in terms of transiting exergy efficiency is investigated and integrated with the transcritical heat pump system. The aim is to investigate the factors that reduce exergy losses and increase the coefficient of performance and exergy efficiency. The contribution of this paper is twofold. First, a three-dimensional numerical analysis of the supercritical CO2 flow simulation in the Tesla turbine in three different geometries is carried out. Second, the effect of the Tesla turbine on the coefficient of performance and exergy efficiency of the heat pump system is investigated. The effect of the rotor speed and disk spacing on the Tesla turbine power, exergy loss, and transiting exergy efficiency is investigated. The results showed that at a lower disk spacing, the turbine produces higher specific power and transiting exergy efficiency. In addition, the coefficient of performance (COP) and exergy efficiency improvement in the heat pump system combined with the Tesla turbine are 9.8% and 28.9% higher than in the conventional transcritical heat pump system, respectively.

시추공식 계간축열 시스템을 이용한 4세대 지역난방 공급 및 효율 개선 연구

The purpose of this study was to compare the conventional Geothermal Source Heat Pump (GSHP) System, with Borehole Thermal Energy Storage (BTES) utilized heat pump system in cost-wise criteria. The consecutive operation of conventional GSHP performance decreased annually, and eventually discharged the purpose of the system. Deploying the BTES system with heat pump, thereby accumulating the low-cost heat energy from the summer season and using it to ease the heating load peak, can manage the presented problem, as well as supply the sufficient and stable amount of heat energy. Additionally the estimated heat pump capacity of conventional GSHP was 7,864 kW and BTES utilized system showed 1,781 kW. The land area occupancy also decreased by 25%. The BTES system can successfully decrease the initial facility investment cost and make efficient use of ground space.

Economic and environmental analysis of ground source heat pump system according to operation methods

A ground source heat pump (GSHP) system can achieve high energy performance than conventional air source heat pump system by using annual stable underground temperature. However, the GSHP system can occurred soil thermal imbalance when the system is used for a long-term operation. Therefore, in order to prevent soil thermal imbalance, increasing the spacing and depth of boreholes and combining GSHP system with auxiliary heat sources are used. However, these methods require large sites and high initial investment. This study proposes an intermittent operation as an alternative to minimize the imbalance by altering the GSHP system. A numerical simulation model that can simultaneously analyze mass and heat transfer in soils was used to accurately analyze the performance of the GSHP system. In addition, the economic analysis and life cycle climate performance (LCCP) were compared based on the numerical analysis results of the GSHP system. Consequently, an appropriate operation method for the system is proposed by comprehensively considering the analysis results for the performance, economics, and environmental impact of the GSHP system according to the operation method. The numerical analysis of the GSHP system showed that the intermittent operation method increased the heat exchange rate of the GSHP system by 15%, compared to the continuous operation method, and the borehole center temperature was higher by 0.8 °C when the system operation concluded. Moreover, the economic analysis results showed that the intermittent operation method could reduce the total cost by up to 18.7% (1,921 USD) compared to the continuous operation method because it can dramatically reduce the initial investment cost. However, as the result of the LCCP analysis for three months, the total emissions increased by up to 11.8% (793 kg CO2e) because the intermittent operation method has a higher energy consumption of the heat pump than the continuous operation method.

Energy, exergy, economic and environmental analysis of a novel direct-expansion solar-assisted flash tank vapor injection heat pump for water heater

Energy, exergy, economic and environmental analysis of a novel direct-expansion solar-assisted flash tank vapor injection heat pump for water heater is conducted by simulation method. Two working modes are designed for the presented system. The solar-assisted mode is recommended for most solar radiation conditions, and the air-source mode maintains more superior performance under extremely low or no solar radiation situations. By utilizing solar energy, the system heating efficiency and capacity can be respectively improved by up to 29.6% and 25.9% under the considered condition. The performance analysis shows that the presented system can respectively enhance the average heating capacity and efficiency by 11.7% and 10.6% in a typical winter day of Lanzhou City, compared with the conventional flash tank vapor injection heat pump system. The exergy analysis expresses that the heat exergy output increases with the solar radiation intensity, while the system exergy efficiency presents an opposite variation trend because of the greater increment of the exergy destruction in the solar collector. The economic analysis indicates that the presented system achieves a payback period of 8 years under the given assumptions. Benefiting from the electricity consumption reduction, the presented system can remarkably reduce the carbon dioxide and air pollution emissions.

Development of a Low-Depth Modular GHX through a Real-Scale Experiment

The global energy sector is aiming to rapidly transform energy systems into those less dependent on fossil fuels to reduce their harmful effects on the climate. Although ground source heat pump (GSHP) systems are more efficient than conventional air-source heat pump (ASHP) systems, the high initial investment cost, particularly for a vertical closed-loop type ground heat exchanger (GHX), makes it difficult to incorporate them into small buildings. This paper proposes a low-depth modular GHX for reducing cost and improving the workability of GSHPs. A modular GHX is a cubical structure comprising tubes and buried using an excavator at a depth 4 m below the ground surface. This GHX is manufactured at a factory, carried by a small truck, and then installed by a small lift or a backhoe such that it can be installed in small buildings or narrow spaces at low depths underground. In this research, the performance and feasibility analyses of modular and vertical GHXs were conducted via a real-scale experiment. The results demonstrate that the modular GHX influences the workability of GSHPs by 91% during the heating period and 70% during the cooling period. In contrast to the conventional HVAC, the modular and vertical GHXs could recover the initial investment costs in 4 years and 10 years, respectively.

Investigation on the performance enhancement of electric vehicle heat pump system with air-to-air regenerative heat exchanger in cold condition

Since the heat pump operation in low ambient temperature requires considerable amount of electric energy, electric vehicles (EVs) suffer from the significant range loss problem in cold regions. In this study, heat pump system with air-to-air regenerative heat exchanger (ARHX) is suggested as a way to improve the energy inefficiency in the ventilation or dehumidification process. In recirculation mode, ARHX reduces heating and dehumidification load by utilizing the temperature difference of two air streams, occurring in the subsequent dehumidification and heating process. In outdoor air mode, ARHX enhances heating performance by recovering the heat from the preconditioned cabin air, which is exhausted to the environment in conventional heat pump system. Heat pump model was built upon an experimentally validated component model and thermal load model. Based on this heat pump model, performance enhancement of the proposed system is investigated in both recirculation and outdoor air mode with various climate conditions. Results confirm that suggested heat pump system decreases heating load and dehumidification load up to 12.3% and 12.9% in recirculation mode and the heating load reduction reaches 20.2% in outdoor air mode. Power consumption of the compressor is saved up to 10.6% in recirculation mode and 55% in outdoor air mode.