Sizing the Supply and return tanks for chilled water system

In summary, the project engineer is trying to size a chilled water system for a factory. They need to identify the high and low temperatures of the input water, the capacity of the plant to cool the input water, and the expected exit temperatures. They also need to talk to senior engineers/management to see if there are any process modifications or expansions that might make the system unworkable or uneconomic.
  • #1
shaheryarbhatti
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Well i am currently working as a project engineer for utilities at my factory .This is my first installation of chilled water system.So would be requiring some help in sizing the Chilled water supply and return tanks.I am attaching the picture along so that the system is easily understandable.
 

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  • #2
I have done a lot of heat and mass balance studies for mills, but none of them have been based on such a bare-bones snapshot.

If you want to size your system, you need to need (at a minimum) to identify the seasonal high and low temps of the input water (then over-design by a margin), identify the capacity of your plant to cool the input water to suitable temperatures (with margins, of course), and identify the expected exit temperatures (again with margins) and see if you can size a system that might meet these requirements.

It would also be a really good idea to talk to senior engineers/management, etc to see if there are any plant expansions or process modifications over the horizon that might tip your project into unworkable/uneconomic territory. In an industrial environment, the bean-counters can ruin your career pretty quickly, even if you gave them conservative parameters initially and they changed the rules after the fact or during implementation.

Good luck.
 
  • #3
Well sorry for the bare diagram because i just wanted to make it simple.I tried to size it but have few issues .Let em first define my systems parameters.

Water in Chilled water tank is at temperature of 5-6 C
Temperature of Water in Return Tank is aroudn 18 C in Summer and around 14-15 C in winter

Chilled water generated is at 1228 m3/h i.e. 307m3/h by each chiller.

System requirement of chilled water is 856m3/h

I designed the Forward tank(140m3/h) with 10 minutes of buffer time that is the case if chillers go on shutdown due to power failure we would have 10 minutes to get system back online.



I calculated that all the time 131 m3 of water is inside the lines.


Now my concern is the Return Tank .How do i size it and on what basis.SHoudl i just keep it 140m3/h or need to size it and on what basis .
 

1. How do I determine the appropriate size for a chilled water supply tank?

The size of a chilled water supply tank is typically determined by calculating the volume of water needed to meet the peak cooling demand of the system. This can be calculated by multiplying the cooling load of the system (in BTUs) by the water volume required to absorb one BTU of heat (usually around 8.33 pounds of water per BTU). It is also important to consider factors such as system pressure and flow rate when sizing the tank.

2. What is the recommended ratio of chilled water return tank size to supply tank size?

The recommended ratio of chilled water return tank size to supply tank size is typically 1:1 or 2:1. This means that for every gallon of water in the supply tank, there should be an equal or double amount in the return tank. This ensures that there is enough water in the system to meet cooling demands and maintain proper system pressure.

3. How do I determine the appropriate size for a chilled water return tank?

The size of a chilled water return tank is typically determined by calculating the volume of water needed to return to the system after it has been circulated through the building and absorbed heat. This can be calculated by multiplying the flow rate of the system (in gallons per minute) by the desired return temperature rise (usually around 10-15 degrees Fahrenheit). It is important to consider the size of the supply tank and the recommended ratio when sizing the return tank.

4. What factors should be considered when sizing chilled water supply and return tanks?

When sizing chilled water supply and return tanks, it is important to consider the peak cooling demand of the system, the flow rate and pressure of the system, the recommended ratio between supply and return tank sizes, and any other specific requirements of the building or equipment. It is also important to ensure that the tanks are large enough to handle any potential variations in cooling demand.

5. Can I use a single tank for both chilled water supply and return?

In most cases, it is not recommended to use a single tank for both chilled water supply and return. This is because the tanks need to be sized differently in order to meet the demands of each function. Additionally, having separate tanks allows for better control and monitoring of the system, as well as easier maintenance and troubleshooting.

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