Plastic pipe heater

[Zrock]

For those of u using black pipe to add some extra heat to your pool.. what works better a tight circle keeping everything together or string it all out?

Sent from my SM-G903W using Tapatalk

 

[mas985]

Heat gain is the same either way because of the physical area. However, heat loss should be a little less if you pack it closer together so there is less temperature difference close to the pipe.

But most people have found that the cost of black poly pipe is more per sq-ft than commercial panels so there is little benefit to making the panels yourself.

 

[Zrock]

That's what I thought... right now the pipe is free until I need it from the next job..

Sent from my SM-G903W using Tapatalk

 

[Zrock]

What would be the best way to control flow using my spare intex filter/pump? Put a valve on inlet to control flow or wire a dimmer switch to a plug and just throttle back the whole motor.

Sent from my SM-G903W using Tapatalk

 

[mas985]

Neither is a good idea. But why do you want to reduce flow rate? You lose less heat with more flow rate.

 

[Zrock]

A buddy that installs water systems said that he used a 1/4 horse motor and a dimmer switch. He slowed the flow enough that it would increase his pool temp by min 6 degrees a day. Water comming out of hose was like bath water. Makes sense slow down the flow so the water can gain some heat. With the flow I have I'm lucky to gain 2 degrees a day. Between the black hose, warm ground and grass heat loss by slowing down the flow would be very minimal

Sent from my SM-G903W using Tapatalk

 

[mas985]

Water comming out of hose was like bath water.

That is bad thing not a good thing.

Slowing down the flow does increase the temperature of the water out of the panels but that does not mean more heat gets into the pool. It is both temperature AND flow rate (amount of water heated) that matter. When you halve the flow rate, temperature of the water out of the panels goes up by less than 2x so in fact, you are transmitting less heat to the pool. It has to do with the fact that heat loss is proportional to the temperature difference of the water and the environment. The higher the temperature of the water out of the panel, the more heat that is lost. The faster the flow rate, the higher the heat transfer efficiency.

 

[danpik]

Whenever people experiment with solar heating they always concentrate on the output water temp. This is the wrong thinking. Heating a pool is all about BTU/hour. A smaller BTU at a higher volume will always work better than a high BTU at a low volume. Another way to look at this is this...Instead of trying to get the water hot in the pipe (which becomes less efficient the hotter the water gets), think of trying to keep the solar collector as cool as possible with the water flow thru the system. As water temp increases, the ability for the water to absorb the heat diminishes. Remember, the system sees the same amount of energy from the sun regardless of water flow. If the water going thru the system is close to the temp of the system with the sun on it then no heat will be gained.

 

[duraleigh]

He slowed the flow enough that it would increase his pool temp by min 6 degrees a day.

Your buddy needs to come on and show us how he did that. Unless he has a kiddie pool, I doubt he did that. Physics always gets in the way, it seems.

 

[Gomez9356]

I can't speak for the physics, but I tried the home made black hose route with restricted flow on my old pool and it didn't work all that well. So when we got the new pool this year we went with a commercial solar heater: Game SolarPRO Above Ground Solar Pool Heaters. I finished filling the pool (8500 gallons) with 60° well water on June 12, and running the pump about 5 hours a day during peak sunshine my water temp was in the mid 80's after only a week. Highs during that time were in the low to mid 90's, lows dropping down to the mid 70's.

 

[Zrock]

While their is lots of good info and probably for the most part right. The theory all sounded right but since i was board and something was just not adding up in my mind i decided to give it a try and slow the water flow had nothing to loose . What did not work in my mind is if the ground temp and air temp are hotter than the water running through the hose then heat loss should be minimal or non existent. The water coming out of the hose was warm ( not as warm as outside temp) and ended up increasing my pool temp by just a hair under 6 degrees a day. My pipe is wrapped as tight as i could get it without putting a kink in it and zip tied tightly together. Its also stick in a corner of the yard where it gets a good 8 hours of sun and up against a bank so it gets the radiant heat from the bank and ground as well.

Im probably running more pipe than the average person. Since i use it at work we buy it by the 300-500ft roll. More than the average person will go out and buy so their was probably still a few hundred feet left in the roll.

 

[mas985]

What did not work in my mind is if the ground temp and air temp are hotter than the water running through the hose then heat loss should be minimal or non existent.

Convection is only one component of heat loss. For solar panels, the major component of heat loss is radiation and it is sky radiation that sucks the heat out of the panels. The sky temperature (other than the direction of the sun) is usually 30 degrees F cooler than the air temperature so a lot of heat is lost to the sky. We had a 92F day the other day and I measured the sky temp with an IR thermometer and it was only 10F. Big difference and where a lot of heat can be lost to radiation.

Also, if you actually measure the ground temperature under the panels, it will be cooler than the panels if the panels are directly on the ground. Remember that the panels are shading the ground and preventing the sun from heating it so ground tends to wick the heat away.

If you can run the water through the tubes faster, you might find the total heat gain to be slightly higher.

 

[jasnovanorder]

Been thinking about doing something like this only putting it up on the garage roof. Roof sees a good 8 hours direct sunlight a day. And with the crazy weather we have had the last few years its really killing our temp. So far this year we are having swings from the 80-90s during the day down to low 50's at night. It will take a few days to get the pool temp to the mid 70's then a cool night will drop it to almost 60. Im sure a solar cover would help also but those are just not in the budget right now

 

[jblizzle]

This comes up so often, I really wish there was a way to once and of all make people realize that a DIY solar system using poly pipe is NOT going to be as efficient or inexpensive as buying the cheap pool solar mats ... when you consider the heat gain in the pool.

The only way the DIY is cost effective is if the pipe is free, but even then you will not add as much heat as the panels unless you use a LOT of pipe.

FYI, I had 2500 feet of this stuff on my roof when we bought my current house that was broken out into about 8-10 parallel circuits, sure it added heat to the pool, but not as much as I wanted and I got tired of dealing with the constant leaks. So I installed 500 sqft of used solar panels myself and gave all the pipe away for some tiny amount of money. We were swimming in 80 degree water in mid-March ... without the use of a solar cover.

By far the cheapest way to warm your pool is to use a solar cover (at least at night) to retain the existing heat.