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

AbstractHeat 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 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 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%.

The Logical Choice of Auxiliary Heat Source for Solar Energy Water Heating System

2012 ◽  
Vol 512-515 ◽  
pp. 303-306
Author(s):  
Xue Lai Liu ◽  
Guan Zhu Wang ◽  
Yong An Li ◽  
Xiao Feng Zhang
Keyword(s):  
Heat Pump ◽  
Operating Cost ◽  
Water System ◽  
Hot Water ◽  
Low Carbon ◽  
Water Heater ◽  
Low Carbon Economy ◽  
Water Heaters ◽  
Air Source Heat Pump ◽  
Heat Pump Water Heater

This article describes the solar hot water system, and establishes the computational model of hot water system. It analyzes the economical efficiency of solar water heaters which equipped with electric water heaters, gas water heaters and air-source heat pump water heaters. The results show that the initial investment of the system which equipped with an electric water heater and a gas water heater is almost, but the operating cost which equipped with a gas water heater system is lower. The operating cost which equipped with an air-source heat pump water heater is the lowest, though the initial investment is the highest. The solar hot water system which equipped with an air-source heat pump water heater has important reference value for going low-carbon economy road in China.

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.

The Solar Energy-Air Source Heat Pump Was Applied to the Hot Water System

2014 ◽  
Vol 587-589 ◽  
pp. 243-246
Author(s):  
Chu Ping Lu ◽  
Kai Ji
Keyword(s):  
Solar Energy ◽  
Heat Pump ◽  
Water System ◽  
Hot Water ◽  
Water Heater ◽  
Circulating Water ◽  
Air Source Heat Pump ◽  
Hot Water Supply ◽  
The City

This paper is as an example of the hot water supply of the hotel in the city,The design of the hot water system is the solar energy and the air source heat pump,includes:the selection calculation of the air source heat pump of the water heater , the selection and calculation of the solar collector,the determination of the thermal storage tank and the determination of the circulating water pump of heat collecting .

scholarly journals Frosting Phenomenon and Frost-Free Technology of Outdoor Air Heat Exchanger for an Air-Source Heat Pump System in China: An Analysis and Review

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2642 ◽  
Author(s):  
Yi Zhang ◽  
Guanmin Zhang ◽  
Aiqun Zhang ◽  
Yinhan Jin ◽  
Ruirui Ru ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Operating Cost ◽  
Heating System ◽  
Coefficient Of Performance ◽  
Outdoor Air ◽  
Pump System ◽  
Heat Pump System ◽  
Reduce Operating Cost ◽  
Air Source Heat Pump

Frost layer on the outdoor air heat exchanger surface in an air-source heat pump (ASHP) can decrease the system coefficient of performance (COP). Although the common defrosting and anti-frosting methods can improve the COP, the periodic defrosting not only reduces the system energy efficiency but also deteriorates the indoor environment. To solve these problems, it is necessary to clearly understand the frosting phenomenon and to achieve the system frost-free operation. This paper focused firstly on the analyses of frosting pathways and frosting maps. Followed by summarizing the characteristics of frost-free technologies. And then the performances of two types of frost-free ASHP (FFASHP) systems were reviewed, and the exergy and economic analysis of a FFASHP heating system were carried out. Finally, the existing problems related to the FFASHP technologies were proposed. Results show that the existing frosting maps need to be further improved. The FFASHP systems can not only achieve continuous frost-free operation but reduce operating cost. And the total COP of the FFASHP heating system is approximately 30–64% higher than that of the conventional ASHP system under the same frosting conditions. However, the investment cost of the FFASHP system increases, and its reliability also needs further field test in a wider frosting environment. In the future, combined with a new frosting map, the control strategy for the FFASHP system should be optimized.

Evaluation of Passive Anti-Fouling Technology Applied to CO2 Heat Pump Water Heaters

2014 ◽  
Author(s):  
Portia Murray ◽  
Stephen J. Harrison ◽  
Ben Stinson
Keyword(s):  
Heat Transfer ◽  
Water Supply ◽  
Heat Pump ◽  
Hot Water ◽  
Normal Operation ◽  
Mineral Deposits ◽  
Reverse Direction ◽  
Water Tank ◽  
Flow Rates ◽  
Water Heaters

Heat pump water heaters are increasing in popularity due to their increased energy efficiency and low environmental impact. This paper describes the experimental testing of a transcritical CO2 heat pump water heater at Queen’s University. A modified 4.5 kW Eco-Cute unit was studied. It sourced heat from a constant temperature water supply and rejected the heat to a 273 litre hot water tank through a gas-cooler. The high temperatures that occur in the gas-cooler of this unit make it ideally suited for natural convection, (i.e., thermosyphon) circulation on the potable water side. This has the potential to reduce pumping power, simplify system operation and design, and increase thermal stratification in the hot water storage tank. This configuration, however, is susceptible to the accumulation of sediments, scale and mineral deposits (i.e., fouling) in geographic regions where high mineral deposits may be present in the water supply. To counteract fouling in these cases, a passive back-flushing system was proposed to prevent the accumulation of deposits on the heat transfer surfaces of the gas-cooler. As hot water is drawn from the system, the cold “mains” supply water is directed through the gas-cooler in the reverse direction of normal operation, scouring the heat transfer surfaces and dissolving deposits of inverse-soluble salts which are a major contributor to fouling on hot heat transfer surfaces. The gas-cooler used was a specially designed unit that, although offering high performance in a compact unit, may be susceptible to the fouling and blockage of the heat transfer passages when used at thermosyphon flow rates. Experiments were conducted to evaluate the effects of the back-flush operation on heat pump performance (i.e., COP) and operation. These were conducted under controlled laboratory conditions, at a range of draw flow rates and temperatures, and are summarized in this paper.

scholarly journals Impact of Boundary Conditions on the Performance Enhancement of Advanced Control Strategies for a Residential Building with a Heat Pump and PV System with Energy Storage

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1413
Author(s):  
Emmanouil Psimopoulos ◽  
Fatemeh Johari ◽  
Chris Bales ◽  
Joakim Widén
Keyword(s):  
Energy Storage ◽  
Boundary Conditions ◽  
Heat Pump ◽  
Simulation Study ◽  
Control Strategies ◽  
Thermal Storage ◽  
Hot Water ◽  
Final Energy ◽  
Advanced Control ◽  
The Impact

Operational control strategies for the heating system of a single-family house with exhaust air heat pump and photovoltaic system and “smart” utilization of energy storage have been developed and evaluated in a simulation study. The main aim and novelty of this study is to evaluate the impact on the benefit of these advanced control strategies in terms of performance (energy use and economic) for a wide range of boundary conditions (country/climate, occupancy and appliance loads). Short-term weather data and historic price data for the same year as well as stochastic occupancy profiles that include the domestic hot water load are used as boundary for a parametric simulation study for the system modeled in detail in TRNSYS 17. Results show that the control using a forecast of dynamic electricity price leads to greater final energy savings than those due to the control using thermal storage for excess PV production in all of the examined locations except Sweden. The impact on self-consumption using thermal storage of heat produced by the heat pump using excess PV production is found to decrease linearly with increasing household electricity for all locations. A reduction in final energy of up to 842 kWh year−1 can be achieved just by the use of these algorithms. The net energy cost for the end-user follows the same trend as for final energy and can result in cost savings up to 175 € year−1 in Germany and Spain due to the use of the advanced control.

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