How does the water flow rate of the air conditioning box coil correspond to the designed cooling capacity?

The designed water flow rate of the air conditioning box coil is determined by the cooling capacity, medium specific heat and supply and return water temperature difference. For ordinary water, it can be checked with Q=ṁ×cp×ΔT, where Q is the heat transfer amount and ṁ is the water mass flow rate. The calculation results should be consistent with the coil selection and the actual available water temperature conditions.

Check the order of magnitude with a unit complete example

Taking 100kW, design water temperature difference of 5K, specific heat of about 4.18kJ/(kg·K) as an example, the mass flow rate is about 4.78kg/s; approximately converted to ordinary water density, the volume flow rate is about 17.2m³/h. If the medium contains antifreeze, the density and specific heat are different, and this conversion factor cannot be used directly.

The known cooling capacity must clearly correspond to which air inlet and outlet conditions and total cooling capacity caliber; the design temperature difference must use the supply and return water temperature difference confirmed by the water system; the medium properties must include the density, specific heat and applicable temperature of water or mixed media. The three items correspond to different calculation inputs, and you cannot just give one cooling capacity number. What water parameters should be confirmed before connecting the air-conditioning box to the cold water system? Please refer toWhat water parameters should be confirmed before connecting the air conditioning box to the cold water system?。

The cooling capacity caliber must be distinguished first

Coil cooling capacity is divided into total cooling capacity, sensible cooling capacity and latent cooling capacity. The total cooling capacity includes sensible heat and latent heat. The sensible cooling capacity corresponds to cooling, and the latent cooling capacity corresponds to dehumidification. When calculating the water flow rate, it should be clear which cooling capacity caliber is used and the air inlet and outlet conditions corresponding to the cooling capacity. If the total cooling capacity is used to calculate the water flow, but the actual operation is mainly based on sensible heat, the water flow may be too large.

How to select the type of surface cooler according to the air inlet and outlet conditions, please refer toHow to select the type of air conditioner cooler according to the air inlet and outlet conditions? . The difference between dehumidification capacity and cooling capacity can be referred toHow to calculate the dehumidification capacity of air conditioning box from the difference in air moisture content?。

Temperature difference selection affects water flow and coil water resistance

The greater the temperature difference between the supply and return water, the smaller the required water flow rate, but as the average water temperature of the coil increases, the heat exchange capacity may decrease. The smaller the temperature difference, the greater the water flow, and the energy consumption of the water pump and pipeline resistance increase. The design temperature difference should be balanced between water system energy savings and coil heat transfer capabilities. Large temperature difference systems need to check whether the number of coil rows and heat exchange area are sufficient.

After the relationship between coil water flow and design cooling capacity is determined, the coil water resistance and on-site available pressure difference must be checked. The water resistance changes with the flow rate. When the flow rate increases, the water resistance increases. How to determine the full pressure of the air-conditioning box fan based on the internal resistance and external demand, please refer toHow is the total pressure of the air conditioning box fan determined by the internal resistance and external demand?。

Calculating the amount of water does not necessarily mean it will be available on site

Also confirm the coil water resistance, valve and line losses, and the available pressure differential of the pump at the corresponding flow rate. The smaller on-site temperature difference may be caused by load, control or hydraulic balance, etc., which cannot be solved mechanically by increasing the amount of water. The operating data should be analyzed together with the air load at that time to avoid misjudgment of partial load status as a selection error.

Whether the diameter of the water pipe in the air conditioning box can be determined directly according to the coil interface, please refer toCan the diameter of the water pipe in the air conditioning box be determined directly based on the coil interface? . Coil water resistance and interface information should be stated in the equipment information.

Recalculation is required when the medium is not ordinary water

When containing antifreeze media such as ethylene glycol, the density and specific heat are different from ordinary water, and the ordinary water coefficient cannot be directly used for water flow conversion. Different ethylene glycol concentrations have different specific heats and densities, and should be recalculated based on the medium data. High concentrations of ethylene glycol can also affect heat transfer efficiency and pump consumption.

For operating pressure, water quality and medium conditions, please refer toWhat water parameters should be confirmed before connecting the air conditioning box to the cold water system? . After the medium changes, the coil material selection and interface may also need to be adjusted.

The calculation results should be checked with the coil selection.

Water flow calculation is part of coil selection and is not an independent step. Coil selection will give the corresponding cooling capacity, water flow, water resistance and air outlet status. If the calculated water flow rate is inconsistent with the coil selection data, the cooling capacity diameter, temperature difference and medium conditions should be checked instead of unilaterally adjusting the water volume.

For the relationship between coil row number and cooling capacity, please refer toWill the greater the number of coil rows in an air-conditioning box, the greater the cooling capacity? . For the influence of wind speed facing the coil, please refer toWhat impact does the coil head-on wind speed have on heat exchange and water entrainment in the air conditioning box?。

Aili industrial supporting equipment

When checking the water coil, Aili Industrial can check the water volume according to the medium and temperature difference given by the project, and retain the design flow rate and water resistance in the interface data. Aili's industrial manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. Coil water flow, water resistance data and interface positions can be corresponded in the same set of supporting materials; non-standard media and temperature difference conditions can be adjusted according to the project water system.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific water flow, water resistance data and delivery scope still need to be confirmed based on the corresponding configuration data and water system design. The actual effect is subject to on-site water system debugging and performance test results.

Submit project parameters:https://ailigy.com/contactus.html

Related questions and answers

Can the water flow rate be calculated directly by knowing the cooling capacity?
The temperature difference between supply and return water and the specific heat and density of the medium are also required. Depending on the temperature difference or medium, the same cooling capacity corresponds to different water flow rates.

The greater the water flow, the greater the cooling capacity of the coil?
uncertain. The increase in water flow will change the heat exchange, but the cooling capacity of the coil is also limited by the water temperature, heat exchange area and air side conditions. The gain is limited after exceeding a certain range.

Can Aili Industrial help check the coil water flow?
The water flow and water resistance can be checked based on the design cooling capacity, supply and return water temperature difference and medium conditions. The specific values ​​must be confirmed based on coil data and water system design.

Related articles

1. What water parameters should be confirmed before connecting the air conditioning box to the cold water system?

2. How to select the type of air conditioner cooler according to the air inlet and outlet conditions?

3. How to calculate the dehumidification capacity of air conditioning box from the difference in air moisture content?

4. Can the diameter of the water pipe in the air conditioning box be determined directly based on the coil interface?

Key points for selection and acceptance inspection