scholarly journals Thermodynamic analysis of a direct expansion solar assisted heat pump water heater

2017 ◽  
Vol 26 (2) ◽  
pp. 110 ◽  
Author(s):  
Masoud Yousefi ◽  
Misagh Moradali
Keyword(s):  
Ambient Temperature ◽  
Heat Pump ◽  
Coefficient Of Performance ◽  
Water Tank ◽  
Direct Expansion ◽  
Water Heater ◽  
Domestic Water ◽  
Heat Pump Water Heater ◽  
Thermodynamic Performance ◽  
Flat Plate Solar Collector

In this paper, the thermodynamic performance of a direct expansion solar assisted heat pump (DX-SAHP), which is used to heat domestic water from 20˚C to 45˚C, is theoretically investigated. The system includes a 3m2 single-cover flat plate solar collector, 0.150m3 water tank and 70m tube immersed in the water tank as a condenser. The effect of various parameters such as radiation on the collector surface, compressor speed and the ambient temperature on the coefficient of performance (COP) are calculated. Results show that obtained COP is considerably more than that of a conventional heat pump water heater when radiation on the collector is high. Also, increasing collector area and reducing compressor speed enhance COP. The same occurs when the ambient temperature increases. For instance, at an ambient temperature of 15˚C and 450 w/m2 irradiation on collector surface, the calculated COP was 6.37.

scholarly journals Experimental Study of a Novel Direct-Expansion Variable Frequency Finned Solar/Air-Assisted Heat Pump Water Heater

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Jing Qin ◽  
Jie Ji ◽  
Wenzhu Huang ◽  
Hong Qin ◽  
Mawufemo Modjinou ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Ambient Temperature ◽  
Heat Pump ◽  
Operating Mode ◽  
Heating Time ◽  
Solar Irradiation ◽  
Variable Frequency ◽  
Direct Expansion ◽  
Water Heater ◽  
Heat Pump Water Heater

A novel direct expansion variable frequency finned solar/air-assisted heat pump water heater was fabricated and tested in the enthalpy difference lab with a solar simulator. A solar/air source evaporator-collector with an automatic lifting glass cover plate was installed on the system. The system could be operated in three modes, namely, air, solar, and dual modes. The effects of the ambient temperature, solar irradiation, compressor frequency, and operating mode on the performance of this system were studied in this paper. The experimental results show that the ambient temperature, solar irradiation, and operating mode almost have no effect on the energy consumption of the compressor. When the ambient temperature and the solar irradiation were increased, the COP was found to increase with decreasing heating time. Also, when the compressor frequency was increased, an increase in the energy consumption of the compressor and the heat gain of the evaporator were noted with a decrease in the heating time.

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.

Performance of Add-On Heat Pump Water Heater (HPWH) Systems and Their Impacts on Electric Utility Loads

2010 ◽  
Author(s):  
Yahya I. Sharaf-Eldeen ◽  
Craig V. Muccio ◽  
Eric Gay
Keyword(s):  
Heat Pump ◽  
Energy Savings ◽  
Electric Energy ◽  
Electric Heating ◽  
Electric Utility ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Energy Output ◽  
Water Heater ◽  
Heat Pump Water Heater

This work involves measurements, analyses, and evaluations of the performance of add-on, Heat Pump Water Heater (HPWH) systems in residential and small commercial applications. Two air-source Heat Pump (HP) systems rated at 7,000- and 12,000-BTU (2.051- and 3.517-kWh), were utilized in this work. The two HPs were retrofitted to two 50-gallon (189.3 liters) electric-resistance storage water-heaters with their electric heating elements removed. A third, standard electric water-heater (EWH), was used for comparison. The testing set-up was fully instrumented for measurements of pertinent parameters, including inlet and outlet water temperatures, inlet and outlet air temperatures of the HPs, temperature and humidity of the air in the surrounding space, volume of water draws out of the storage heater tanks, as well as electric energy consumptions of the systems. Several performance measures were used in this work, including the Coefficient of Performance (COP), which is a measure of the instantaneous energy output in comparison with the energy input; Energy Factor (EF), which is an average measure of the COP taken over extended periods of time; and the First Hour Rating (FHR), which is a measure of the maximum volume of hot water that a storage type water-heater can supply to a residence within an hour. The results obtained clearly indicate that, HPWH systems are much more efficient as compared to standard EWHs. While the average value of the EF for a standard EWH is close to 1.0, the HPWH systems yield EFs averaging more than 2.00, resulting in annual energy savings averaging more than 50%. The results also showed that, HPWH systems are effective at reducing utility peak demand-loads, in addition to providing substantial cost savings to consumers.

Control strategy and experimental analysis of a direct-expansion solar-assisted heat pump water heater with R134a

Energy ◽  
2018 ◽  
Vol 145 ◽  
pp. 17-24 ◽  
Author(s):  
Xiangqiang Kong ◽  
Kailin Jiang ◽  
Shandong Dong ◽  
Ying Li ◽  
Jianbo Li
Keyword(s):  
Heat Pump ◽  
Control Strategy ◽  
Experimental Analysis ◽  
Direct Expansion ◽  
Water Heater ◽  
Heat Pump Water Heater

Performance Comparison among Heat Pump Water Heaters Working with R32, R134a and the Mixture of R32/R134a

2012 ◽  
Vol 512-515 ◽  
pp. 1295-1298
Author(s):  
De Feng Ding ◽  
Shi Jie Liu ◽  
Chao Yu Zheng ◽  
Wen Sheng Yu ◽  
Wu Chen
Keyword(s):  
Power Consumption ◽  
Heat Pump ◽  
Average Power ◽  
Input Power ◽  
Performance Comparison ◽  
Coefficient Of Performance ◽  
Water Heater ◽  
Heat Pump Water Heater ◽  
Discharge Temperature ◽  
Average Power Consumption

A general air-source heat pump water heater originally designed to work with R134a was reconstructed as experimental rig for performance studies on systems using different refrigerants including R32, R134a and the mixture of R32/R134a which mass ratio is 1:5. Experimental results showed that the power consumption of the heat pump water heater charged individually with R32 would greatly exceed the system’s original pre-set maximum input power. When the leaving water temperature was increased from 18°C to 58°C, the average discharge temperature of the heat pump charged with R32/R134a mixture was 13.6% higher than that with R134a. The average power consumption of the heat pump with R134a was 253.5W less than that with R32/R134a mixture. However, the average COP (Coefficient of Performance) obtained by that with R32/R134a mixture was 0.83 higher than that with R134a.

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