Technical help: How to calculate the circulating water volume

It is recommended to refer to GB 50050-2007 \"Code for Design of Industrial Circulating Cooling Water Treatment\", as it may contain the information you need.

Accurate calculation of the circulating water volume is necessary in order to determine the heat load of the process units. The processes themselves specify the amount of circulating water required for each unit; thereafter, it is possible to calculate the evaporation losses, wind-induced losses, and discharge losses in the circulating water plant using the design standards for such plants in chemical enterprises. Finally, by determining the amount of water that needs to be replenished, it becomes possible to account for all components involved in the system, including the circulating water tanks, suction tanks, circulating water pumps, system pipes, and dosing systems!

It needs to be calculated based on the amount of heat that needs to be removed

You must know some basic parameters, such as inlet and outlet temperatures, system capacity, concentration ratio, water addition volume, wastewater discharge volume, etc. Without these basic design parameters, it is impossible to carry out calculations.

This post was last edited by li*ch1968 on 2009-5-17 at 11:26. Those who are not designers find it really troublesome to do the calculations; it requires a lot of effort.

I would also like to learn about this topic. Could any fellow sailor provide some detailed calculations, such as how to determine the capacity of a water intake tank and what precautions should be taken?

The information you’ve provided is quite general, which makes it difficult to give reasonable suggestions. However, based on the details you’ve mentioned, I would suggest the following: 1. The selection of pumps for a circulating water system should be determined based on the operating conditions of the system. For example, if the system is large and supplies several devices, the flow rate of each pump needs to be chosen taking into account the possibility that those devices may operate independently. As for the pump’s head pressure, it must be determined by considering all aspects of the system as a whole, ensuring proper balance in terms of water level and pressure. However, after making the selection, it is necessary to determine whether the flow rate and head when multiple water pumps are operated in parallel can meet the requirements regarding total water volume and water pressure ； 2. If by \"pool\" is meant the water intake pool, you can refer to the design specifications for chemical process circulating water systems. The spacing between the water intake pipes, the minimum depth of submersion, and the distance from the water inlets to the pool walls must all meet the specified requirements. The minimum volume should be at least equal to the water intake capacity of the maximum pump operating for 5 minutes; however, the pool should not be designed to be too large, as an excessive amount of water in the system makes it difficult to increase the concentration ratio ； 3. The piping system must meet the requirements regarding water volume and pressure of the water supply system, while minimizing the amount of water stored in the system.

What is the purpose of circulating water? As for the cooling water for the equipment, the equipment documentation should specify the volume of water circulating (if such information is available); if not, flow meters and thermometers should be used to actually measure the flow rate and the temperature difference between the inlet and outlet of each piece of equipment, to determine whether these values meet the process requirements (cooling water valves are always available for the equipment). Measure the flow rate of the dust removal water and check whether the dust removal efficiency meets the process requirements, and then conduct statistics. To determine the pressure loss, check the values shown on the pressure gauge on the equipment and, if available, the pressure gauge at the pump outlet; this can help to preliminarily assess whether the pipeline design is unreasonable. If you ask someone to do the calculations, even professional plumbing designers from design firms may not be able to provide accurate results. The formula for calculating the flow rate of water in low-temperature systems is: Q = maximum cooling capacity × 1000 / density of circulating water × specific heat of circulating water × temperature difference between inlet and outlet. A loss of cooling capacity of 15% is generally assumed. —I copied it from the design institute’s documents; I’m not sure if it’s correct. The key issue is that the theoretical cooling capacity, or the cooling capacity of the equipment, often differs from the actual required value. The calculations may result in distortions.

Refer to the \"Chemical Process Handbook\" and the first volume of the \"Process Piping Installation Design Handbook\" titled Design and Calculation; they contain detailed explanations of the relevant processes. I work in a design institute, and we use these two books as the basis for our designs. The main aspects include determining the process flow, selecting the diameter of the pipes for fluid flow, calculating the pressure loss associated with pipes and valves, and then selecting the pump!

This post was last edited by cdpulin on 2009-11-2 at 13:17. The circulation volume can be determined by checking how many pumps are in use and at what capacity they operate； Residual water volume – A more accurate method is to shut off both the wastewater discharge and the water supply when there is no thermal load, add a certain amount of positive phosphorus, circulate the system several times, and then determine the phosphorus concentration; from this value, the residual water volume can be calculated. Alternatively, in operational mode, KCl can be added and the concentration of potassium ions measured; the residual water volume can also be calculated by converting these concentrations ； Whether to optimize it – well, that’s a bit more complicated. It’s reasonable to keep the water volume at around half of the circulation volume. The diameter of the pipes must be determined in accordance with relevant standards; however, in practice, an ultrasonic flow meter can be used to measure the flow rate and velocity within the pipes. Typically, the flow velocity should not be lower than 1.0 m/s, with a minimum of 0.8 m/s. Similarly, for heat exchangers as well, it is necessary to measure the flow rate and temperature. If the flow rate is high and the temperature difference is large, problems are likely to occur; on the other hand, if the flow rate is too high and the temperature difference is small, it represents a waste.