Indoor thermal environment in a rural dwelling heated by air-source heat pump air-conditioner

In hot summers, air conditioning (AC) and mechanical ventilation (such as fans) are used as cooling modes that strongly influence the resultant indoor environment, like thermal comfort and air quality in the shops of a Nanning arcade street (qilou). The air circulation mode in shops greatly affects the indoor thermal environment and level of air freshness. The approaches for effectively improving the indoor thermal comfort and air quality are developed in qilou street shops with air-conditioner in a humid and hot region in southern China. Consequently, the purpose of this study is to assess different ventilation schemes in order to identify the best one. By using two indices, i.e., the predicted mean vote (PMV) and the age of air (AoA), in situ measurement and numerical simulation are conducted to investigate humans’ thermal comfort in extreme summer. Then, the indoor thermal comfort and AoA levels in summer under three different ventilation schemes (upper-inlet–upper-outlet, upper-inlet–bottom-outlet, and side-inlet–side-outlet) are comparatively analyzed through numerical computations of the indoor thermal environment. The results show that the upper-inlet–upper-outlet mode of the AC ventilation scheme led to the creation of a favorable air quality and comfortable thermal environment inside the shop, which will help designers understand the influence of the ventilation scheme on the indoor thermal comfort and health environment.

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Underfloor Heating Using Room Air Conditioners with Air Source Heat Pump in a Foundation Insulation House

Energies ◽

10.3390/en14217034 ◽

2021 ◽

Vol 14 (21) ◽

pp. 7034

Author(s):

Hiroki Ikeda ◽

Yasushi Ooi ◽

Takashi Nakaya

Keyword(s):

Heat Loss ◽

Heat Pump ◽

Thermal Environment ◽

Heat Pumps ◽

Foundation Slab ◽

Air Conditioners ◽

Air Source Heat Pump ◽

Reduce Heat Loss ◽

Long Time ◽

Detached House

A good thermal environment is important in a place where occupants stay for a long time. Since heating a house consumes a lot of energy, an energy-efficient heating method will be required. Then, by combining a heat pump and underfloor heating, there is a possibility that both thermal comfort and energy saving can be achieved. The survey was conducted on a detached house located in Nagano Prefecture, Japan. The average outside air temperature was 4.2 °C. This study investigated the indoor thermal environment, evaluated the operating performance of the heat pump, and calculated the heat load by two-dimensional analysis. More than 80% of the subjects were satisfied with the thermal environment and the neutral temperature was 18.9 °C. In the operation of the heat pump, defrost operation was confirmed, but the average COP was 2.9, and it operated efficiently. In addition, the heat loss from the foundation slab was examined. Proper insulation placement has shown the potential to reduce heat loss. In conclusion, the use of heat pumps as a heat source has been shown to be efficient even in cold climates, and this study supports the construction of new heating methods.

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The Experimental Study of Thermodynamic Performance on R407C Air-Conditioner Hot Water Combined Unit

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.467-469.549 ◽

2011 ◽

Vol 467-469 ◽

pp. 549-553

Author(s):

Hong Song Hu ◽

Fang Wang ◽

Jian Zhong Yu ◽

Wu Hao

Keyword(s):

Heat Pump ◽

Paper Analysis ◽

Hot Water ◽

Air Conditioner ◽

Water Heater ◽

Operation Conditions ◽

Air Source Heat Pump ◽

Heat Pump Water Heater ◽

Environmental Friendly ◽

Thermodynamic Performance

This paper analysis on the design and the test of an air-conditioner hot water combined unit using environmental friendly refrigerant R407C. Firstly the research status of the system is elaborated for air-source heat pump water heater simply. Then the principle and structure are described on an air-conditioner heat pump followed by a water heater at different running modes and different operation conditions. The hot water experiments of the unit in three seasons have been tested and researched in a multi-functional environmental chamber. Some analysis of the unit’s thermodynamic performance is carried out from the test data for improving such kind of machine afterward.

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Experimental Study on Characteristics of False Defrosting for Split Air Source Heat Pump

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.220-223.585 ◽

2012 ◽

Vol 220-223 ◽

pp. 585-591

Author(s):

Rui Chao Tang ◽

Zhi Tao Han ◽

Er Kang Zhang ◽

Shu Guang Liu ◽

Hai Quan Zhang ◽

...

Keyword(s):

Experimental Study ◽

Heat Exchanger ◽

Heat Pump ◽

Control Method ◽

Temperature Sensors ◽

Air Conditioner ◽

Air Source Heat Pump ◽

Shaft Power ◽

Discharge Pressure ◽

Two Temperature

Detailed experimental study on the characteristics of false defrosting of a split type air-source heat pump (ASHP) has been made. The results show that the false defrosting is seriously detrimental to ASHP by comparing varied parameters of compressor such as shaft power, suction and discharge pressure, etc. in normal defrosting and false defrosting. This paper also analyzes a common defrosting control method for air conditioner of split ASHP room, i.e., with two temperature sensors set on indoor heat exchanger, the operating principle thereof and drawbacks in terms of causing false defrosting.

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A TOPSIS optimization for the indoor thermal environment through oscillating airflow generated from a cassette split type air conditioner

Indoor and Built Environment ◽

10.1177/1420326x20939305 ◽

2020 ◽

pp. 1420326X2093930

Author(s):

Yunqing Fan

Keyword(s):

Thermal Performance ◽

Cfd Simulation ◽

Control Method ◽

Thermal Environment ◽

Vertical Section ◽

Thermal Preference ◽

Air Conditioner ◽

Indoor Thermal Environment ◽

Swing Angle ◽

The Impact

This study evaluates the feasibility of a control method, ‘the Technique for Order of Preference by Similarity to Ideal Solution’ (TOPSIS) for the optimization of the subzone thermal environment by optimizing the oscillating airflow generated from a cassette split type air conditioner. To address the quasi-dynamic thermal comfort problems, various operation swinging angles of the louvre in the supply opening of an air conditioner and swinging periods were investigated by computational fluid dynamics (CFD) simulation. The impact of air supply control strategies (louvres movement) on the indoor thermal environment was evaluated by multi-criteria operation under quasi-dynamic conditions. The operation parameters were shown to have significantly improved the deviation in thermal uniformity by 16.5% and thermal preference by 7.6%. A 40 s swing period and wider swing angles for the operation of the inner louvre would satisfy the thermal uniformity rather than other alternatives. A shorter swing period <20 s is insufficient to allow perfect airflow mixing at the vertical section. For individual target mode such as the room corner, the thermal performance is more sensitive to the swing angle than the swing period; by increasing the swing angle to ±60° to enhance thermal preference, a 24.1% increase in the overall thermal performance would be achieved.

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

10.21203/rs.3.rs-255294/v1 ◽

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.

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

Theoretical and Applied Climatology ◽

10.1007/s00704-021-03673-2 ◽

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.

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