Calculation formula for air conditioning water flow | Capacity calculation of air conditioning water system

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1. Calculation rules for air conditioning water system pipelines

The calculation of air conditioning water system pipelines mainly involves water flow rate, pipe diameter, and pump head, which need to be accurately calculated according to the system type and actual load. 1. The calculation of water flow in air conditioning water systems varies depending on the system type. For a fixed water volume system, the total water flow is directly calculated based on the maximum load of the system to ensure that peak demand is met. The calculation of variable water volume systems is slightly more complicated, using the formula $W=\ frac {n1n2Q} {c (\ rho (t_h - t_j))} $, where $W $is the total amount of cold water (unit $m ³/s $), $Q $is the total load of each air-conditioned room under design conditions (unit $kW $), $c $is the specific heat capacity of water (usually taken as $4.19 kJ/(kg ·℃) $), $\ rho $is the density of water (taken as $1000 kg/m ³ $), $t_h $and $t_j $respectively represent the average return water temperature and supply water temperature (unit $℃ $), and $n1 $$n2 $is the synchronous usage coefficient, reflecting the probability of equipment running simultaneously

2. The selection of pipe diameter directly affects water flow efficiency and system stability. For general water pipes, the formula $D=\ sqrt {\ frac {L} {0.785 \ times3600 \ times V} $is the basis, $L $is the water flow rate of the pipe section, and $V $is the allowable flow rate. In practice, the flow rate needs to match the pipe diameter: the recommended flow rate between DN100 and DN250 is about $1.5m/s. If it is less than DN100, it should be lower than $1.0m/s, and if it is greater than DN250, it can be appropriately increased.

Formula for calculating air conditioning water flow rate

If the pipe diameter or flow rate does not match, it can easily lead to increased noise or energy consumption. The calculation of the condensate pipe relies on the simultaneous solution of the flow formula Q=v · A, and the pipe diameter D is determined by the flow rate Q, slope i, and roughness coefficient n. The roughness coefficient $n $varies depending on the material: steel pipes are commonly $0.012 $, while plastic pipes are slightly lower; The slope $i $needs to be ensured to be no less than $0.3 \% $, and $i ≥ 0.4 \% $is preferred to improve drainage efficiency and avoid water accumulation. When designing, you can also refer to the flowmeter for quick selection. The wall thickness calculation of refrigerant pipes (copper pipes) involves pressure safety, and the commonly used Barlow formula is $t=[(P × oD)/(2 σ a+0.8P)]+α $, where $t $is the wall thickness ($mm $), $P $is the working pressure ($MPa $), $oD $is the outer diameter ($mm $), $σ a $is the allowable stress of the material ($N/mm ² $), and $α $is the corrosion allowance ($0 $for copper pipes). This can ensure that the pipeline does not deform or leak under high pressure

3. The determination of the pump head requires covering all the resistance of the system. Taking the water-cooled screw unit as an example, the head of the chilled water pump includes: the resistance of the evaporator water in the refrigeration unit (usually $5-7mH ₂ O $, refer to the product sample), the resistance of the end equipment surface cooler (similar to $5-7mH ₂ O $), the resistance of the return water filter (about $3-5mH ₂ O $), the resistance of the water separator and collector (each $3mH ₂ O $), and the loss of resistance along the water pipeline (generally $7-10mH ₂ O

Calculation formula for air conditioning water flow | Capacity calculation of air conditioning water system

1. Calculation rules for air conditioning water system pipelines

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