Efficient Hot & Cold water combination for bathing

In summary: Generally, when water is heated to a higher temperature than it is comfortable for, we add cold water to bring it down to comfortable temperature. Sometimes we heat the water to a higher temperature first and add cold water, and sometimes we add cold water to the already heated water. The process of doing this is called mixing. The best combination of hot and cold water (quantities and temperature) is usually the one that heats the water to the temperature that the body is comfortable at. This is usually done by adding some cold water to the hot water. The process of doing this is called mixing. Energy losses are proportional to temperature. The basic principle here should be to generate water that is just hot enough for use without needing to dilute with
  • #1
djsourabh
69
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Generally for bathing purpose, we heat water to higher temperature say T1 than the temperature at which body is comfortable say T0 (is T0 = 70 degree Celsius?) & add some quantity of cold water to it to have the temperature of water = T0. Is the process energy efficient?
What is the best combination of hot & cold water (quantities & temperature) so that least amount of energy is spent?
eg, say we require 10 litres of water at temp T0 for comfortable bathing.
So how do we do it, heat 7 litres of water to temp T1 & add 3 litres of cold water at temp T2 to get 10 litres of water at temp T0. But this may not be the energy efficient combination, we might heat 10 litres of water to T0 & spend lesser energy than the above case. So what are the equations & how to know which would be the best combination?
 
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  • #2
Energy losses are proportional to temperature. The basic principle here should be to generate water that is just hot enough for use without needing to dilute with cold water. This is especially true where hot water is stored for some time waiting for use. This also has the safety advantage of not scalding children.

The only reason to run at a higher temperature than needed is when the capacity of the storage is less than the volume of hot water immediately required.

I believe your mixing calculations should be based on the mass of water, not on volume.
 
  • #3
Baluncore said:
Energy losses are proportional to temperature. The basic principle here should be to generate water that is just hot enough for use without needing to dilute with cold water This is especially true where hot water is stored for some time waiting for use. This also has the safety advantage of not scalding children.

The only reason to run at a higher temperature than needed is when the capacity of the storage is less than the volume of hot water immediately required.

I believe your mixing calculations should be based on the mass of water, not on volume.

Do you mean that we spend least energy in the case you mentioned? (The basic principle here should be to generate water that is just hot enough for use without needing to dilute with cold water) ?? It will be very helpful if I get equations to support that.
 
  • #4
Yes, just warm enough is more efficient than hot.
It is probably best analysed from the lost energy viewpoint.

The hotter the water in the reservoir is, the faster it will lose heat. It will do that even if you do not use any water. That is a major inefficiency. Get better thermal insulation on the tank.

When you use hot water it passes along a pipe that absorbs heat and then radiates proportional to the elevation in temperature. Use low thermal capacity pipe material and insulate all hot water pipes.

If you use a greater volume of warm water, than if it were hotter, it will still only heat the pipe to a lower water temperature once. If small quantities of water are used often, pipe thermal loss will be significant. Put the hot water reservoir near the kitchen sink. The distance to a bath or shower can be greater since, more water is used, less often.
 
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1. How does an efficient hot and cold water combination work for bathing?

An efficient hot and cold water combination for bathing works by combining both hot and cold water streams through a mixing valve to achieve the desired water temperature. The mixing valve is typically controlled by a single lever or knob that allows the user to adjust the ratio of hot and cold water to achieve the desired temperature.

2. What are the benefits of an efficient hot and cold water combination for bathing?

The main benefit of an efficient hot and cold water combination for bathing is the ability to quickly and easily adjust the water temperature to your preference. This not only saves time, but also reduces water and energy consumption as you do not need to waste water while waiting for the perfect temperature. It also ensures a consistent and comfortable bathing experience.

3. Are there any downsides to using an efficient hot and cold water combination for bathing?

One potential downside is that the mixing valve may malfunction or develop leaks over time, which can be costly to repair. Additionally, some people may prefer the traditional method of manually adjusting hot and cold water faucets to achieve the desired temperature. However, with proper maintenance and installation, these downsides can be minimized.

4. How can I ensure an efficient hot and cold water combination for bathing in my home?

To ensure an efficient hot and cold water combination for bathing in your home, it is important to have a high-quality mixing valve installed by a professional plumber. Regular maintenance and repair of the mixing valve can also help maintain its efficiency. Additionally, using low-flow showerheads and faucets can further reduce water and energy consumption.

5. Can an efficient hot and cold water combination be used in all types of bathrooms?

Yes, an efficient hot and cold water combination can be used in all types of bathrooms, including those with limited space. There are various types and sizes of mixing valves available, making it possible to install them in small and large bathrooms alike. It is important to consult with a professional plumber to determine the best type of mixing valve for your specific bathroom layout and needs.

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