Thermostatic Mixing Valve: Flow Rates and Energy Conservation

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In summary, the problem is determining the flow rates for hot and cold water supplies connected to a tap through a Termostatic Mixing Valve. The hot water is at 60°c and the cold water is at 10°c, while the tap supplies water at 41°c and a flow rate of 0.17 l/s. Various attempts have been made to find the solution, including considering the First Law and conservation of mass principles. The total flow rate must equal the sum of the two flow rates and mixing flows is handled similarly to mixing temperatures.
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TomStar
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Heres the problem.

I have a tap supplying water at 41°c and at a flow rate of 0.17 l/s. The tap is connected to a Termostatic Mixing Valve (TMV) with a hot and cold water supply.

The hot water is at 60°c and the cold water is being supplied at 10°c.

What are the flow rates for the hot water supply and the cold water supply?

Have tried many things to find the answer but still no luck, if someone can please let me know a formula would be very greatful!
 
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  • #2
Hint: If you have 1 liter of water at 20 C and 2 liters of water at 30 C and mix them, what is the final temperature? Mixing flows is handled in a similar manner.

With this problem you have the total flow rate. Therefore the sum of the two flow rates must equal the total flow.
 
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  • #3
You can also look at the problem from a First Law standpoint. You have a control volume which is the valve. You have energy entering from two pipes. Energy leaves through another pipe. Is there any work being done? Is there any heat transfer? You also have to consider conservation of mass.
 

FAQ: Thermostatic Mixing Valve: Flow Rates and Energy Conservation

What is the "Thermostatic Mixing Problem"?

The Thermostatic Mixing Problem refers to the challenge of maintaining a consistent and safe water temperature in a plumbing system that uses both hot and cold water sources.

Why is the Thermostatic Mixing Problem important?

This problem is important because it directly impacts the safety and comfort of individuals using the plumbing system. If the water temperature is too high, it can cause scalding, and if it is too low, it can promote the growth of harmful bacteria.

What are the potential consequences of not addressing the Thermostatic Mixing Problem?

If the Thermostatic Mixing Problem is not addressed, it can lead to serious injuries, such as burns or exposure to harmful bacteria. It can also result in legal liability for building owners or managers.

How is the Thermostatic Mixing Problem typically solved?

The Thermostatic Mixing Problem is typically solved by installing a thermostatic mixing valve, which automatically adjusts the hot and cold water flow to maintain a safe and consistent temperature. Regular maintenance and testing of the valve are also necessary to ensure its effectiveness.

Are there any regulations or standards related to the Thermostatic Mixing Problem?

Yes, there are regulations and standards that address the Thermostatic Mixing Problem. For example, in the United States, the Occupational Safety and Health Administration (OSHA) has specific requirements for hot water temperature in workplaces, and the American Society of Sanitary Engineering (ASSE) has standards for thermostatic mixing valves.

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