scholarly journals Evaluation of the coefficient of performance of an air source heat pump unit and an air to water heat pump

2021 ◽  
Vol 32 (1) ◽  
pp. 27-40
Author(s):  
S. Tangwe ◽  
K. Kusakana
Keyword(s):  
Heat Pump ◽  
Thermal Energy ◽  
Pressure Sensors ◽  
Electrical Energy ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Water Heaters ◽  
Air Source Heat Pump ◽  
Heat Pump Unit ◽  
The Difference

Air source heat pump (ASHP) water heaters are efficient devices for sanitary hot water heating. The coefficient of performance (COP) of the air to water heat pump (AWHP) is constantly lower than that of the corresponding ASHP unit. The study focused on determining the COP of both the ASHP unit and the AWHP. This was achieved by the implementation of both experimental and simulation methods, with the help of a data acquisition system and the REFPROP software. The system comprised of a 1.2 kW split type ASHP unit and a 150 L high pressure geyser. A power meter, flow meters, temperature sensors, pressure sensors, ambient temperature and relative humidity sensor were installed at precise locations on the split type AWHP. Controlled volumes of 150, 50 and 100 L were drawn off from the AWHP during the morning, afternoon and evening for a year. The average COP for the summer and winter, in terms of the input electrical and output thermal energies of the AWHP were 3.02 and 2.30. The COPs of the ASHP unit, in terms of the change in the enthalpies of the refrigerant at the inlet and the outlet of the condenser and the evaporator, were 3.52 and 2.65 respectively. The study showed that the difference between the COP of the ASHP unit and that of the AWHP could be ascribed to the electrical energy consumed by the fan and the water circulation pump during the vapour compression refrigeration cycles. The work provides an energy optimisation opportunity to the manufacturers of this technology, helping to enhance the efficiency and COP of ASHP water heaters. Highlights The COPt of the ASHP unit was higher than the COPe of the AWHP. The COPe of the AWHP was the ratio of the input electrical energy consumed and the output thermal energy gained by the stored water. The COPt of the ASHP unit was enthalpies-dependent and a function of inlet and outlet enthalpies of the evaporator and condenser. The inlet and outlet refrigerant temperatures profiles of the condenser confirmed thermal energy dissipation.

Simulative Study on Solar-Assisted Air Source Heat Pump System

2013 ◽  
Vol 671-674 ◽  
pp. 2141-2144 ◽  
Author(s):  
Qiang Wang ◽  
Feng Zhen Liu ◽  
Li Jun Hou ◽  
Jian Hua Gao
Keyword(s):  
Heat Pump ◽  
Operating Conditions ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Pump Unit ◽  
Pump System ◽  
Heat Pump System ◽  
Air Source Heat Pump ◽  
Heat Pump Unit ◽  
The Stability

A solar assisted air source heat pump unit is designed. The mathematical model of the unit is established and two hybrid operating conditions of the system are simulated. The simulative studying results shows that in winter the solar assisted air source heat pump unit can make full use of solar energy and the coefficient of performance (COP) of air source heat pump can be improved. In summer the cooling heat of air source heat pump could be recovered to improve the stability of solar hot water collector and the COP of the air source heat pump unit is greatly improved. The performance of solar assisted air source heat pump unit is better than that of with no solar assisted air source heat pump.

scholarly journals Comparison of Transcritical CO2 and Conventional Refrigerant Heat Pump Water Heaters for Domestic Applications

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 479
Author(s):  
Ignacio Paniagua ◽  
Ángel Álvaro ◽  
Javier Martín ◽  
Celina Fernández ◽  
Rafael Carlier
Keyword(s):  
Heat Pump ◽  
Thermodynamic Cycle ◽  
Heat Pumps ◽  
Design Tool ◽  
Operating Conditions ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Ambient Conditions ◽  
Water Heater ◽  
Water Heaters

Although CO 2 as refrigerant is well known for having the lowest global warming potential (GWP), and commercial domestic heat pump water heater systems exist, its long expected wide spread use has not fully unfolded. Indeed, CO 2 poses some technological difficulties with respect to conventional refrigerants, but currently, these difficulties have been largely overcome. Numerous studies show that CO 2 heat pump water heaters can improve the coefficient of performance (COP) of conventional ones in the given conditions. In this study, the performances of transcritical CO 2 and R410A heat pump water heaters were compared for an integrated nearly zero-energy building (NZEB) application. The thermodynamic cycle of two commercial systems were modelled integrating experimental data, and these models were then used to analyse both heat pumps receiving and producing hot water at equal temperatures, operating at the same ambient temperature. Within the range of operation of the system, it is unclear which would achieve the better COP, as it depends critically on the conditions of operation, which in turn depend on the ambient conditions and especially on the actual use of the water. Technology changes on each side of the line of equal performance conditions of operation (EPOC), a useful design tool developed in the study. The transcritical CO 2 is more sensitive to operating conditions, and thus offers greater flexibility to the designer, as it allows improving performance by optimising the global system design.

Analysis of Domestic Hot Water Production Efficiency for Detached Houses

2015 ◽  
Vol 797 ◽  
pp. 185-191
Author(s):  
Arkadiusz Gużda ◽  
Norbert Szmolke
Keyword(s):  
Heat Pump ◽  
Production Efficiency ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Water Production ◽  
Water Heater ◽  
Domestic Hot Water ◽  
Air Source Heat Pump ◽  
Heat Pump Water Heater ◽  
Detached House

The article compares two means for domestic hot water production (DHW) for a detached house that is using gas boiler with a closed combustion chamber and air source heat pump water heater (ASHPWH). An analysis of domestic hot water production using an air source heat pump was made taking into account coefficient of performance listed according to the new BS EN 16147 standard. The analysis of outlay related to the investment and operating costs was also performed. Ultimately, the more profitable choice for domestic hot water production was made.

Prediction of coefficient of performance and simulation design of an air-source heat pump water heater

2017 ◽  
Vol 15 (03) ◽  
pp. 378-394 ◽  
Author(s):  
Stephen Loh Tangwe ◽  
Michael Simon ◽  
Edson Leroy Meyer
Keyword(s):  
Electrical Energy ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Ambient Conditions ◽  
Water Heater ◽  
Content Type ◽  
Air Source Heat Pump ◽  
Significant Difference ◽  
Air Speed ◽  
Heating Up

Purpose The purpose of this study was to build and develop mathematical models correlating ambient conditions and electrical energy to the coefficient of performance (COP) of an air-source heat pump (ASHP) water heater. This study also aimed to design a simulation application to compute the COP under different heating up scenarios, and to calculate the mean significant difference under the specified scenarios by using a statistical method. Design/methodology/approach A data acquisition system was designed with respect to the required sensors and data loggers on the basis of the experimental setup. The two critical scenarios (with hot water draws and without hot water draws) during the heating up cycles were analyzed. Both mathematical models and the simulation application were developed using the analyzed data. Findings The predictors showed a direct linear relationship to the COP under the no successive hot water draws scenario, while they exhibited a linear relationship with a negative gradient to the COP under the simultaneous draws scenario. Both scenarios showed the ambient conditions to be the primary factor, and the weight of importance of the contribution to the COP was five times more in the scenario of simultaneous hot water draws than in the other scenario. The average COP of the ASHP water heater was better during a heating cycle with simultaneous hot water draws but demonstrated no mean significant difference from the other scenario. Research limitations/implications There was a need to include other prediction parameters such as air speed, difference in condenser temperature and difference in compressor temperature, which could help improve model accuracy. However, these were excluded because of insufficient funding for the purchase of additional temperature sensors and an air speed transducer. Practical implications The research was conducted in a normal middle-income family home, and all the results were obtained from the collected data from the data acquisition system. Moreover, the experiment was very feasible because the conduction of the study did not interfere with the activities of the house, as occupants were able to carry out their activities as usual. Social implications This paper attempts to justify the system efficiency under different heating up scenarios. Based on the mathematical model, the performance of the system could be determined all year round and the payback period could be easily evaluated. Finally, from the study, homeowners could see the value of the efficiency of the technology, as they could easily compute its performance on the basis of the ambient conditions at their location. Originality/value This is the first research on the mathematical modeling of the COP of an ASHP water heater using ambient conditions and electrical energy as the predictors and by using surface fitting multi-linear regression. Further, the novelty is the design of the simulation application for a Simulink environment to compute the performance from real-time data.

Performance optimization of an air source heat pump water heater using mathematical modelling

2015 ◽  
Vol 26 (1) ◽  
pp. 96-105 ◽  
Author(s):  
Stephen Tangwe ◽  
Michael Simon ◽  
Edson L. Meyer ◽  
Sampson Mwampheli ◽  
Golden Makaka
Keyword(s):  
Ambient Temperature ◽  
Heat Pump ◽  
Performance Optimization ◽  
Rate Of Change ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Water Tank ◽  
Water Heater ◽  
Conservation Of Energy ◽  
Air Source Heat Pump

In South Africa, there is an ongoing constraint on the electricity supply at the national grid to meet the demand. Eskom is implementing various measures such as the Integrated Demand Management and the promotion and encouragement of the use of energy efficient devices like an Air Source Heat pump (ASHP) water heater to replace the high electrical energy consuming conventional geysers for sanitary hot water production. The ASHP water heater market is fast gaining maturity. A critical mathematical model can lead to performance optimization of the systems that will further result in the conservation of energy and significant reduction in global warming potential. The ASHP water heater comprises of an ASHP unit and a hot water storage tank. In this study, a data acquisition system (DAS) was designed and built which monitored the energy used by the geyser and the whole building, the temperature at the evaporator, condenser, tank outlet hot water, tank inlet cold water, the ambient temperature and relative humidity in the vicinity of the ASHP evaporator. It is also worthy to mention that the DAS also included to a flow meter and two additional temperature sensors that measured the volume of water heated and inlet and outlet water temperature of the ASHP. This work focused on using the mathematical equation for the Coefficient of Performance (COP) of an ideal Carnot’s heat pump (CHP) water heater to develop basic computation in M-file of MATLAB software in order to model the system based on two reservoir temperatures: evaporator temperatures (Tevp) of 0°C to 40°C (approximated to ambient temperature, Ta) and condenser temperatures (TCon) set at 50°C, 55°C and 60°C (approximated to the hot water set temperature of 50°C, 55°C and 60°C) respectively. Finally, an analytical comparison of a CHP water heater to the practical ASHP water heater was conducted on a hot water set point temperature of 55°C. From the modelling results, it can be deduced that at 0°C Tevp, the COP was 5.96 and 2.63 for CHP and ASHP water heater respectively, at a hot water set temperature of 55°C. Above 20°C Tevp, the rate of change of COP increased exponentially for the ideal CHP system, but was constant at 0.01/°C for the practically modelled ASHP water heater.

scholarly journals Performance assessment between a ground coupled and air source heat pump used for domestic hot water preparation

2019 ◽  
Vol 111 ◽  
pp. 06075
Author(s):  
Calin Sebarchievici
Keyword(s):  
Heat Pump ◽  
Simulation Models ◽  
Electrical Energy ◽  
Heat Pumps ◽  
Hot Water ◽  
Pump System ◽  
Heat Pump System ◽  
Domestic Hot Water ◽  
Air Source Heat Pump ◽  
Systems Simulation

A ground-coupled heat pump system (GCHP) and an air source heat pump (ASHP) driven by photovoltaic panels are used to provide domestic hot preparation for a NZEB house. The experimental measurements are used to test both the heat pump models in the same conditions of water temperature and volume of domestic hot water. A comparative analysis of the two heat pumps for domestic hot water preparation is performed. In addition, using the software TRNSYS (Transient Systems Simulation), two numerical simulation models of thermal and electrical energy consumption in DHW mode are developed. Finally, the simulations obtained using TRNSYS software are analysed and compared to the experimental data.

scholarly journals Impact of Compressor Drive System Efficiency on Air Source Heat Pump Performance for Heating Hot Water

2020 ◽  
Vol 12 (24) ◽  
pp. 10521
Author(s):  
Mariusz Szreder ◽  
Marek Miara
Keyword(s):  
Heat Pump ◽  
Air Temperature ◽  
Heating System ◽  
Operating Conditions ◽  
Drive System ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Air Source Heat Pump ◽  
Heating Capacity ◽  
The Impact

A standard Polish household with a central heating system powered by a solid fuel furnace was chosen as a case study. The modular Air Source Heat Pump (ASHP) was used to heat the hot water outside the heating season. In this article comparative studies of the impact of the compressor drive system used on the energy efficiency of the heat pump have been carried out in operating conditions. The ASHP heating capacity and coefficient of performance (COP) were determined for the outside air temperature in the range from 7 to 22 °C by heating the water in the tank to a temperature above 50 °C. For the case of a fixed speed compressor, average heating capacity in the range 2.7−3.1 kW and COP values in the range 3.2−4.6 depending on the evaporator supply air temperature were obtained. Similarly, for the inverter compressor, the average heating capacity in the range of 2.7−5.1 kW was obtained for the frequency in the range of 30–90 Hz and COP in the range 4.2−5.7, respectively. On cool days, the average heating capacity of the heat pump decreases by 12%. For the simultaneous operation of two compressors with comparable heating capacity, lower COP values were obtained by 20%.

scholarly journals Feasibility study of exploiting gearbox oil temperature of wind turbine for improving a heat pump water heater in cold areas

2021 ◽  
pp. 54-62
Author(s):  
Refat Mohammed Abdullah Eshaq ◽  
Eryi Hu ◽  
Ameen A Alshaba ◽  
Aiman A.M Alsenwi
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Fuel Consumption ◽  
Heat Pump ◽  
Thermal Energy ◽  
Mechanical Energy ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Solar Collectors ◽  
Water Heater

Purpose. Feasibility of completely dispensing with solar collectors (SCs) that are used in heat pump (HP) systems for hot water in cold areas. Methodology. Since the temperature of gearbox oil is relatively high, lots of heat can be exploited. Therefore, the recovery of this unutilized heat from gearbox oil temperature of a wind turbine shows a promising solution in improving heat pump (HP) efficiency for hot water especially in cold environment or the district that is located in the north of our planet where the solar energy is very low. This investigation focuses on the feasibility of direct conversion of mechanical energy harvested from the wind speed into thermal energy by exploiting only the friction phenomenon inside the gearbox of the wind turbine by completely dispensing with solar collectors (SCs) that are used in combined solar assisted heat pump (SAHP) because the SCs have various problems, such as large heat loss, low efficiency, freezing and tube-burst, which may limit their applications. Findings. Results show that the wind turbine can provide the power required for HP during the winter season due to high wind speed in Xuzhou city, Jiangsu, China particularly in January. At best, coefficient of performance (COP) may reach 4.08 without SCs, thus the suggested system ensures high COP in addition to decrease in the fuel consumption by 23.25%. Originality. Wind power driven HPs have been suggested in many pervious papers as a sustainable measure to provide heat to a house; however, to improve COP of HP system, we suggest using a wind turbine to directly drive the HP and exploit gearbox oil temperature in an assistant heat exchanger installed after the HP evaporator for providing additional thermal energy to refrigerant R12 and cooling the gearbox oil. Practical value. The coefficient of performance (COP) of HP has reached 4.08 without SCs, so the suggested system demonstrates high COP in addition to the reduced fuel consumption. Approximately 23.25% of energy could be saved using this novel system compared to a fuel water heater for DHW.

scholarly journals Observational evaluation of outdoor cooling potential of air-source heat pump water heaters

2021 ◽  
Author(s):  
Kazuki Yamaguchi ◽  
Tomohiko Ihara ◽  
Yukihiro Kikegawa
Keyword(s):  
Wind Speed ◽  
Heat Pump ◽  
Thermal Environment ◽  
Hot Water ◽  
Influential Factor ◽  
Water Supply Systems ◽  
Outdoor Air ◽  
Water Heaters ◽  
Air Source Heat Pump ◽  
The Impact

Abstract Heat pump water heaters are highly efficient hot water supply systems that effectively utilize the heat of outdoor air via heat pump technology. Many studies have been conducted to optimize the design and operation of heat pump water heaters from the perspective of climate change mitigation. Air-source heat pump water heaters, which absorb heat from the outdoor air and emit cold exhaust, can also be expected to alleviate the urban heat island effect; however, this has not been studied extensively. To estimate the impact of cold exhaust on building-scale climate, we conducted a multipoint measurement of the outdoor thermal environment around a low-rise apartment building equipped with air-source heat pump water heaters, in both summer and winter. Observations showed a substantial cooling effect that decreased air temperatures by 1°C within the site boundary on summer nights when multiple heat pump water heaters operated concurrently. The analysis revealed that the sensitivity of the ambient temperatures to cold exhaust depends strongly on local atmospheric conditions. The most influential factor was the wind direction: the sensitivity increased significantly when the exhaust outlet location was at the lee side of the building. Naturally, the wind speed also affected the sensitivity, which tended to be higher when the wind speed was lower. The convective stability near the ground surface, however, showed no significant influence over the sensitivity.

scholarly journals Low to very high temperature thermal energy recycling – 3 case studies

2021 ◽  
Vol 313 ◽  
pp. 09001
Author(s):  
Arne Høeg ◽  
Tor-Martin Tveit
Keyword(s):  
High Temperature ◽  
Heat Source ◽  
Case Studies ◽  
Heat Pump ◽  
Thermal Energy ◽  
West Coast ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
The West ◽  
Very High

In this paper we present three case studies of the installation of a stirling-cycle high temperature heat pump applied to recycling thermal energy including steam generation. Many industries have heat demand at temperatures above 100°C and often the preferred energy carrier is steam. The optimal integration of a heat pump can be determined by investigating the thermal need of the process with pinch technology. For many industries, the pinch temperature is too high for conventional heat pumps. We present a heat pump solution that can recycle thermal energy and deliver this to a heat source up to 200°C, as hot water or steam. The heat pump can be integrated in a thermodynamic efficient way placing the sink and source in-between the pinch temperature. The working medium is a gas throughout the process cycle, with no evaporation or condensation. Thus, the process can auto-adjust to temperature variations and achieve very high efficiencies compared to the Carnot heat pump cycle. The coefficient of performance (COP) of the heat pump vary with the sink/source temperatures as the temperature fraction varies. Another important feature is that the medium has both a global warming potential (GWP) and ozone depletion potential (ODP) of zero. The thermodynamics of the heat pump is explained in more detail in the introduction section. The first installation is at a dairy plant on the west coast of Norway. In this installation, the heat pump provides cooling at 0-5°C and converts this heat into hot water at 120°C. The second installation is also at a dairy in Norway. Here the heat pump cools the ammonia from the cooling compressors at about 25-30°C and converts the heat to hot water at 110C°. The third installation is at a beverage plant on the west coast of Norway. Here the heat pump is providing cooling to compressors and other equipment. The final temperature of the heat source varies from 20-70°C. The heat is converted into steam at 168°C. In the case study sections, the installations are discussed in more details, together with the performance and a discussion of the experiences with the technology.

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