Practical estimation of chilled water pump head

Here is the resistance of a closed air-conditioning system, because it is a commonly used system. 1. Chiller resistance: provided by the unit manufacturer, usually 60 ~ 100kPa. 2. Pipeline resistance: including frictional resistance, local resistance, where the unit length of the frictional resistance than the group is subject to technical and economic comparison. If the value of the small diameter, the initial investment in the province, but the pump energy consumption is large; if the value of small on the contrary. The current design of the cold water pipe than the group should be controlled in the 150 ~ 200Pa / m range, larger diameter, the value may be smaller. 3. Air conditioning device end resistance: the end of the type of fan coil unit, modular air conditioners and so on. Their resistance is based on the design of the air into and out of the air-conditioning coil parameters, cooling capacity, water temperature, etc. by the manufacturer through the coil configuration calculation provided, many rated conditions can be found in the product samples. This resistance is generally in the range of 20 ~ 50kPa. 4. Regulating valve resistance: air-conditioned room is always required to control room temperature, air conditioning through the end of the waterway set the electric two-way valve is to achieve a means of room temperature control. Two-way valve specifications by the valve fully open when the flow capacity and allowable pressure drop to choose. If this allows the pressure drop value is large, the valve control performance is good; if the value is small, poor control performance. The pressure drop at full opening of the valve as a percentage of the total pressure drop across the branch is called the valve power. Water system design requires valve authority S> 0.3, so, two-way valve to allow the pressure drop is generally not less than 40kPa. Based on the above, it is possible to roughly estimate the pressure loss of a 100-m high-rise building air-conditioning water system, that is, the lift required for a circulating water pump: 1. Chiller resistance: 80 kPa (8 m water column) Road resistance: Take the decontamination of the chiller room, water traps, manifolds and pipes, etc., with a resistance of 50 kPa. Take the length of the piping on the transmission side 300m and specific friction 200 Pa / m, the frictional resistance is 300 * 200 = 60000 Pa = 60 kPa; if the partial resistance of transmission and distribution side is taken as 50% of the friction resistance, the local resistance is 60 kPa * 0.5 = 30 kPa; the total resistance of the system pipeline is 50 kPa and 60 kPa + 30 kPa = 140 kPa (14m water column) 3. Air conditioning end device resistance: The resistance of the combined air conditioner is generally larger than the resistance of the fan coil, so the resistance of the former is 45 kPa (4.5 water column). 4. Two- Resistance: Take 40 kPa (0.4 water column). 5. Therefore, the sum of the resistance of each part of the water system is: 80 kPa + 140 kPa + 45 kPa + 40 kPa = 305 kPa (30.5 m water column) 6. Pump head: Take the safety factor of 10%, then lift H = 30.5m * 1.1 = 33.55m. Based on the above estimation results, it is possible to basically grasp the range of pressure loss value of the air-conditioning water system of similar scale building, in particular, to prevent over-conservative calculation without excessively estimating the system pressure loss, Cause energy waste.

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