Cooling of Overhead Water Tank in Summer

Insulate the tank?

If the wet-bulb temperature is favorable, you could use evaporative cooling, maybe a simple spray system.

ya the wet bulb temprature is favorable

Well, that is the source of coolth, then. What is needed is in ingenious way to use it.

Cover the tank with wet blankets.

Your Killin ME.........LOL

If the outside air temperature is really what is getting the water hot then I don't have anything to add to comments #1 and #2.

If sunlight is also making the water tank hot then consider adding a sun shield to comments #1 and #2.

Why you have a water tank on the roof? What supplies the water to the tank, the rain, a pipe from the city water system? To lower the temperature of the water in the tank (to about 45 degrees C) you can build a structure over the tank, so the sun doesn't fall directly, still, the water in the tank will have the ambient temperature. You might try a fabric wrapped around the tank. When wet, the energy to evaporate the water in the fabric will lower, a bit, the temperature in the tank. How much? No idea! If the water comes from the city water system (from the ground) make a branch directly to your needing place and you might have an even lower (14-20 degrees) temperature water. If none of the solutions works, you need a cooler type on the pipe coming from the tank.

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I wrote before reading the other comments. Sorry for redundancy

the tank is getting fill from city water system with the help of a pump . water entering the tank is too hot and u need to keep it flowing for period of time in order to get it cool down . what u think if i place a heat exchanger at the inlet of the tank ?

Install a simple cooling tower onto the supply line from the city. If tank is insulated properly and shaded, should be all you need to do.

Rather than try to cool the whole tank, you might like to make a small "Coolgarie" safe that cools the water as it is delivered into the house.

Coolgardie works on the evaporation principal. An outer container (say a perforated 200l drum) has 20m of copper water pipe coiled inside it and the interspace filled with charcoal blocks or similar porous material. The water supply flows through that pipe.

Air flow through the perforations enables evaporative cooling to happen. A slow but constant "drip" onto the porous material maintains the moisture levels for evaporation to continue.

Provides two benefits. You immediately have your cool water and as hotter water is drawn in, there is the thermal mass of the pipe and wet charcoal to cool that flow.

Large versions of these were used in outback as refrigerators on properties.

Yep! Remember them well.

Before people used refrigerators or they couldn't afford one, the coolgardie safe was used extensively in the hot Australian summers to keep dairy products and meat..........and boy the used to work well.

This reminded me of something similar............the hessian bag containing water that you used to hang on the font of the car.........not in front of the radiator..........and in summer that water used to be icy cold. Here is a photograph of one:

45C ambient ?

What's wet Bulb? More likely 28C.

So all you need is a small Falling Film Cooling Tower and a couple of miniature recirculating pumps .

i am looking for a costless design ? Must be kidding!

ga

Insulate using simple thermocol or wood or wide leaves of Palm Tree.

I suspect it is more likely to be the pipes and the water in the pipes which is getting hot rather than the tank which will have considerable thermal mass.

Yes, shade the tank by all means, but also shade and insulate the pipes!

Simple way is use few buckets ,fill the water and allow it to cool in the shaded bath room. Other way is in summer water heater which is installed inside the bath room is rarely used . Use this water . Both these methods does not need any extra energy consumption and does not invlove any cost except the capital cost to buy a bucket.

mrswamy,

You said it! Use the water through the Storage water heater in the bathroom that is already cold (indoor, with heater electric power off). This is exactly what we are used to do in Muscat where the summer outdoor temperatures exceed 55degC.

I also do the same here in Muscat.

Simple and economical way would be cover the tank top with jute bags or hessain cloth. and sprinkle water ocasionaly to keep the fabric wet. Due to evaporation of water, tank water will remain cool. Sprinkling system can be similar to garden sprinklers.

What is your water tank made of? Is the city water line coming in accessible and exposed to sunlight? What is the water temperature at night after a few hours with no sunlight?

I suspect you are fighting radiant heat gain from the sun. You need a radiant barrier coating on the line and the tank.

We have dropped the surface temperature of a painted metal roof by 76-degrees.

We have dropped the air temperature coming into buildings by as much as 25-degrees just be coating the rooftop AC unit and a little metal ductwork. Many other examples on our website. Our URL is on my page.

I have coated small galvanized water pump storage tanks at homes. it dropped the water temperature by 30-degrees (on a hot summer day) . Prior to coating, they also had to let it run for around 15-minutes before it got cool. You could not touch the tank prior in the afternoon. Now it is cool all the time.

Dear Mr.dadima,

What is the Volume of the tank, and how much water it is holding.?

Splashing in to the tank, after heat exchanger, will result in formation of VAPOUR which is to be vented out - and this means LOSS OF WATER.

During winter the water will be much chiller.

What about the cooling medium and circulation for the heat exchanger.?

Best thing, as suggested by the other CR4 MEMBER, Insulate the tank,and Distribution pipe line, no running expense. Insulation will take care in winter also.

Pl. post the information - what was your final decision.

DHAYANANDHAN.S

<...looking for a costless design...>

This is in the domain of the Turboencabulator, transparent alumin(i)um, etc.

Good luck with that...