Fountain pump head simple estimate method

HVAC pump selection: usually selected than the number of ns in the 130 ~ 150 centrifugal water pump, water pump flow should be 1.1 to 1.2 times the additional flow of chillers (single take 1.1, the two parallel take 1.2 according to the budget Can be taken roughly every 100 meters along the length of the loss of 5mH2O, pump head (mH2O):

Hmax =△ P1 +△ P2 + 0.05L (1 + K)

△ P1 is the water pressure drop of the chiller evaporator.

△ P2 is the water pressure drop of one of the air-conditioning end devices connected in parallel in the loop with the greatest loss of water pressure.

L is the tube length of the most adverse loop

K is the most unfavorable part of the loop resistance equivalent length and the sum of the total length and straight tube ratio, when the most adverse loop is longer K value of 0.2 to 0.3, the worst of the short loop when the K value of 0.4 to 0.6

----- Chilled water pump head useful budget method -----

What we are talking about here is the resistance of closed-circuit air-conditioning cold water systems, which are commonly used systems.

1. Chillers resistance: from the unit manufacturer supply, usually 60 ~ 100kPa.

2. Pipeline resistance: including friction resistance, part of the resistance, during which the friction resistance per unit length of friction than the Moroccan group depends on the technical and economic comparison. If the value of large diameter is small, the initial investment in the province, but the pump running energy consumption; if the value is small and vice versa. The current planning of the cold water pipe than the friction group should be controlled in the 150 ~ 200Pa / m range, larger diameter, the value can be smaller.

3. Air-conditioning end device resistance: the end of the type of equipment with fan coil units, modular air conditioners and so on. Their resistance is based on planning the air into and out of the air conditioning coil parameters, cooling capacity, water temperature, etc. by the manufacturer through the coil after the supply of equipment, a lot of additional conditions in the product samples can be found on the value. This resistance is usually in the range of 20 to 50 kPa.

4. Control valve resistance: air-conditioned room is always the need to control room temperature, air conditioning equipment through the end of the waterway to set the electric two-way control valve is a means of achieving room temperature control. Two-way valve by the valve when the standard fully open to the flow and the pressure drop to allow the selection. If this allows a large value of the pressure drop, the valve control function is good; if the value is small, the control function is poor. When the valve is fully open the pressure drop accounted for the percentage of the total pressure drop is called the valve weight. Water system planning requirements of valve power S> 0.3, so the two-way valve to allow pressure drop is usually not less than 40kPa.
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