Estimation Method 1: Selection of HVAC Pumps: Centrifugal water pumps with a specific rotation ns of 130 to 150 are usually selected. The flow rate of the pump should be 1.1 to 1.2 times of the rated flow rate of the chiller (1.1 for single and parallel connection for two 1.2 Estimated approximate loss of 5mH2O per meter of pipe length, mH2O: Hmax = ΔP1 + ΔP2 + 0.05L (1 + K) ΔP1 is the water pressure drop of the chiller evaporator ΔP2 is the water pressure drop of one unit with the largest loss of hydraulic pressure in each loop of the air conditioner in parallel, L is the tube length of the most adverse loop, K is the sum of the local resistance equivalent lengths in the most unfavorable loop And the ratio of the total length of straight pipe, when the most adverse ring is longer when the K value of 0.2 to 0.3, the most unfavorable ring is short when the K value of 0.4 to 0.6 to estimate Method 2: Here is the closed air-conditioning cold water system Of the resistance, because this system is the amount of commonly used systems. 1. Chiller resistance: provided by the unit manufacturer, usually 60 ~ 100kPa. 2. Pipeline resistance: including frictional resistance, local resistance, where the friction unit length Resistance is more than the group based on technical and economic comparison. Larger values ​​are small diameter, the initial investment in the province, but the pump energy consumption is large; if the value is small then the current design of cold water pipe than the group should be controlled in the 150 ~ 200Pa / m range, the diameter of the more 3. The air conditioner end device resistance: the end device type fan coil unit, modular air conditioner, etc. Their resistance is based on the design of the air into and out of the air-conditioning coil parameters , Cold, water temperature difference by the manufacturer after the coil configuration calculation provided, many rated condition values ​​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 the room temperature, through the end of the water in the air-conditioning installation of electric two-way control valve is a means of room temperature control. Two-way valve specifications by the valve opening capacity and allowable pressure drop If the allowable value of the pressure drop is large, the control performance of the valve is good, and if the value is small, the control performance is poor.The pressure drop at the full opening of the valve which accounts for the total pressure drop of the branch is called the valve weight Water system Timing requirements valve authority S> 0.3, then, two-way valve to allow the pressure drop is generally not less than 40kPa. Based on the above, you can roughly estimate a high-rise building about 100m high pressure water system water pressure loss, that is The required lift of the circulating pump: 1. Chiller resistance: take 80 kPa (8m water column); 2. Pipeline resistance: take the resistance of the decontamination, sump, water trap and piping in the freezer room as 50 kPa; take the pipeline length of the distribution side 300m and the specific friction of 200 Pa / m, then the frictional resistance is 300 * 200 = 60000 Pa = 60 kPa; Considering the local resistance of the transmission side is 50% of the frictional resistance The local resistance is 60 kPa * 0.5 = 30 kPa; the total resistance of the system piping is 50 kPa + 60 kPa + 30 kPa = 140 kPa (14m water column); 3. Air conditioning end device resistance: The resistance of the combined air conditioner is generally lower than that of the fan Coil resistance, so take the former resistance of 45 kPa (4.5 water column); 4. Two-way control valve resistance: Take 40 kPa (0.4 water column). 5. Thus, 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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