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Sixth, design and selection of air source heat pump unit

Sixth, design and selection of air source heat pump unit

2019-05-24

Air Source Heat Pump Heating Design and Construction Guide Chapter 1 Air Source Heat Pump Basics Chapter 6 Design and Selection of Air Source Heat Pump Units

(1) Heat pump unit capacity correction
The capacity of the air-to-water heat pump unit should be determined according to the total cold and heat load of the air-conditioning system, and generally depends on the larger of the cold and heat loads. The cooling (heating) capacity of the unit is related to the defrosting situation, in addition to the close relationship with the ambient air temperature.

It must be noted that the heating capacity in the performance or characteristic curve of the unit provided by the manufacturer is generally the nominal heating capacity under standard working conditions, which is an instantaneous value, and does not take into account the heat loss caused by defrost. Therefore, when determining the actual heating capacity Q (kW) of the unit in winter, it should be corrected according to the outdoor air conditioning calculation temperature and defrost frequency:


Q=q×K1×K2

Where: Q——heat production (kW) under actual operating conditions of the unit;

Q——heat production under standard product conditions (standard operating conditions: outdoor air dry bulb temperature 7 ° C, wet bulb temperature 6 ° C) (kW);
K1——Use the regional outdoor air conditioner to calculate the dry bulb temperature correction coefficient, and select according to the product sample;
K2——The correction factor of the unit fuser should be corrected according to the data provided by the manufacturer; when there is no data, it can be derated by 0.9 per hour and 0.8 times twice.

(2) Conversion with the International System of Units

The number of air conditioners refers to the input power, that is, 1 horse (horse) = 735W (watt). Including the press, fan motor and electronic control part. Due to the difference in the specific system and electronic control design of different brands, the output cooling capacity is also different, so the cooling capacity is calculated by the output power. Generally speaking, the cooling capacity of one horse is roughly 2000 calories, and the international unit conversion should be multiplied by 1.162, so the cooling capacity is 2000×1.162=2324W. Here, W (Watt) means the cooling capacity, which is the national standard unit (the auxiliary unit is also used in kilowatts (kW).

What we need to choose the air source heat pump is the heating or cooling capacity at the actual temperature. According to the heat supply or cooling capacity, the “pile” is a power unit, which is unscientific to use. Since everyone is using it, we introduce its conversion relationship.

According to 1 horsepower = 735W (watt) and energy efficiency ratio (heating, cooling coefficient) formula ε = Q / W
Number of horses = Q / (ε × 735)

For example, calculate the required heating capacity to be 20 kW, and the energy efficiency coefficient is assumed to be 3 (related to outdoor temperature) 20000/(3×735)=9

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