Karim's 1500gal dream reef

[karimwassef]

One more variable - airflow. The wind in Texas comes in strongest from the south and since the sunroom faces south, the low intake vents will allow cool air in from the bottom southern face (with the big doors) and flow up to the top exhaust before the wall that the tank is against.

The backroom also has exhaust fans to vent the hot air buildup when the door is closed.

I still haven't decided if I can to run vents from the southern face to the backroom to get some fresh southern air running to the back.

 

[jccaclimber]

Karim, while I was doing mass flow calculations with you the other day we negliany cooling from the water loop. Of course with your water temp higher than your desired air temp I'm not sure how much cooling you'll be able to push that direction.

The point of capacitance made above is a good one. While your desired water temperature is below the wet bulb temperature for parts of the day, the 24 hour average being lower combined with enough waster volume may save you.

Your air injection will of course be either consuming AC cooled air, or adding to the heat load during peak summer hours.

 

[karimwassef]

They're close... 78 vs 83

The air temperature and humidity is for my comfort AND to avoid the sunroom glass ceiling turning into an internal cloud and rain device as condensation dogs up the glass and then starts dripping. It would be a shame to go to all this trouble only to have to use an umbrella indoors.

I would say that 83F indoors air could be tolerable if the humidity was low enough.

 

[jccaclimber]

Check that psychometric chart, but I'm guessing it will be cheaper to pull it down a couple degrees than significantly dry out the air.

 

[wertoiuy]

My understanding has always been that the groundwater and therefore ground are at the same temperature of the average temperature year-round. This is because of water's high specific heat. I am not sure how far you have to go to achieve this though, groundwater in Dallas is like 500+ feet. I know permafrost doesn't go more than a few feet, because earth is such a good insulator. Average temperature in Dallas is like 64 degrees, so I think the temperature at 10 feet down would be lower than 78 degrees. If you have measured it at that, disregard what I am saying.

 

[karimwassef]

I have a reference somewhere in an earlier post that has the Dallas ground temp 10ft down at 74-78 winter-summer. I'll have to find it.

 

[jccaclimber]

^So do I, although I found one just now putting it at 68F. Of course that also put groundwater at 500 to 1000 feet down, so that may be why.

 

[Subsea]

My ground water here in Hays County is the Trinity Aquifier at 900’, The water comes up at 78 degrees. When I lived in DeRidder, La, my groundwater was the Chico’s Aquifier with groundwater at 10’. The water came out at 68 degrees. Because of the constant temperature of this water, I used it as a once thru tube and shell heat exchanger. Put 500’ of poly tubing in a 20G tub. Run cooling water from the Aquifier thru tubing and discharge into a pond. Run system water in and out of tub.

Perhaps you could use the lake as your cooling water?

 

[karimwassef]

I'm moving away from the lake. The lake is also controlled by the army corps of engineers... no access

I doubt I'll strike water

but I'm only assuming 78F for the outlet temperature after going through 400ft of pipe.

 

[Subsea]

Your project is very intriguing. I would indeed like to visit to see the whole system. I have not studied on it in detail. I have a niece that lives in Plano, Tx. Would that be anywhere close to you?

I have too many irons in the fire. Getting my 450G outside system on line and winterized before Thanksgiving is my first priority.

 

[Subsea]

I'm moving away from the lake. The lake is also controlled by the army corps of engineers... no access

I doubt I'll strike water

but I'm only assuming 78F for the outlet temperature after going through 400ft of pipe.

You will not know until you do it.

With respect to heat transfer, the most restrictive thing to heat transfer is the boundary layer at the surface. In the case of water inside the tubes, turbulent flow would best serve heat transfer. On the outside of the tube is dry dirt with air spaces between grains. The boundary layer on exterior of tube is air and dirt, both of which are insulator.
I think you will be disappointed, unless you drill a well and use water on both sides to transfer heat.

I still think you should consider a salt water wading pool with spray fountains or cascading steps of water into the pool. Use LED accent lighting.

 

[karimwassef]

Plano is just 20mins away from Prosper. Welcome to visit and help!

My original idea was to use a septic tank underground full of water and run the pipes inside it... but that would make laying the pipes difficult and more expensive.

Then I thought of encasing them in concrete (slab underneath with sides then fill), but maintenance would be impossible vs. very hard.

Then I considered making a concrete floor and sides with pipes inside, then just fill with wet sand, then cover up with dirt to the top. Maybe even have a pipe that constantly replenished water from my waste RODI there.

In the end, I went with just pipes in wet sand given that the heat diffusion over many hours should overcome the insulation between the grains.

 

[Subsea]

When I cooled a 500G system I ran 68 degree Chicot Aquifier water at 1GPM with a 5 degree increase in temperature. Heat transfer was 1GPM times 60 minutes per hour times 8.34 lbs/gallon times 5 degrees temperature change. At 2,500 BTU/Hr that is 1/5 HP chiller.

To accomplish this, I anchored down two 100’ rolls of 1/4” irrigation tubing inside a 10G Rubbermade container. After about a year, stuff started growing on outside and I removed tubing and jetted off with hig pressure washer. The septic tank idea could be used to increase your system volume thereby dampening temperature swings.

 

[Subsea]

Plano is just 20mins away from Prosper. Welcome to visit and help!

My original idea was to use a septic tank underground full of water and run the pipes inside it... but that would make laying the pipes difficult and more expensive.

Then I thought of encasing them in concrete (slab underneath with sides then fill), but maintenance would be impossible vs. very hard.

Then I considered making a concrete floor and sides with pipes inside, then just fill with wet sand, then cover up with dirt to the top. Maybe even have a pipe that constantly replenished water from my waste RODI there.

In the end, I went with just pipes in wet sand given that the heat diffusion over many hours should overcome the insulation between the grains.

Initially, I misunderstood what was being cooled in underground pipes. I toured a home in Natchez, Miss that used air intake ducts under shaded oaks and ran this air underground into the basement. The center of the house was a tower with vents at the top, allowing warmer air to vent thereby drawing cooler air in. Different wings of the house went off in four directions. At the top of the tower, was a solor collector of light using mirrors to direct sun beams and then using quartz to diffuse this light where desired.

Considering what you said about the small heat transfer of air not being restricted by the ground side, makes me think that you will not get your return on investment.
On one of your post, you mentioned that you expected it to be too hot in the middle of the day. Use your roof vents during the heat of the day. Hot air in the sunroom will not effect system water temperature near as much as sunlight. If you want it cooler during the middle of the day, close your ridge vents and use air conditioner to handle comfort in the sunroom.
Even though the system water and the sunroom air temperature effect each other, they should be dealt with separately.

 

[karimwassef]

True. The air temp is driven by the greenhouse effect and solar radiation. I'm cooling the air just for my comfort. The water temp is driven by solar radiation. The greenhouse air temp will not likely change it much.

That's why I have a large air loop and then a completely separate large water loop. They serve different functions.

 

[Subsea]

I have thought some more on your system requirements. Not knowing how far you have already constucted, I make some generalizations.

I suggest you lease/purchase a swamp cooler. New cost about $2500. Run system water thru swamp cooler. This will cool both air and system water. Discharge air into sun room and up thru vents in ceiling. Salt creep can easily be rectified by adjusting flow rate of cooling water. When guest come to visit, lower fan speed on swamp cooler to lowest setting. After one summer, if this does not work, terminate rental lease.

 

[karimwassef]

I haven't broken ground yet so I have plenty of time to think things through and I appreciate all the help.

I originally thought of swamp coolers since they're so commonly used for greenhouse cooling. Unfortunately, that would have been perfect in a dry desert climate but not dallas. Humidity is 60% in the summer and we get lots of warm wet rain. It's actually really important to keep my air dry, especially in the sunroom side. I'm concerned about making it rain with high humidity hitting the glass. In the back room, high humidity will destroy most equipment, so I even considered adding a dehumidifier... even if that increases air temperature.

When I was thinking of the big fans blowing over the sump water, the intent was to cool the water only and expel the moist air out. I also have plans for a large DIY external evaporative cooler like they use for pools. The idea is to keep the water cool, but also keep the air dry.

<a href="http://s1062.photobucket.com/user/karimwassef/media/Designs/0_zpsd0dword6.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/Designs/0_zpsd0dword6.jpg" border="0" alt=" photo 0_zpsd0dword6.jpg"></a>

 

[Subsea]

Yes, I follow your biggest concern is the comfort of the sunroom temperature and humidity.

 

[Subsea]

For certain, evaporative cooling is the most economical method to cool water or air. I have seen them lower 95 degree air to 85 degrees in the middle of the GOM on a drilling rig. Humidity was well above 85 percent.

If you use a remote cooling tower to cool off water and vent moisture to the athmosphere, you would address both of your concerns. For sunroom temperature control, use a large enough heat pump to handle both sides. I was recently quoted $11K for a 4 ton unit that self regulated its operation. At a 17 SEER, it would use DC inverter technology and run slower at reduced load. No matter what else you do, at times you will need HVAC. I suggest you try that alone before doing all of the passive cooling. Use your remote evaporative cooling tower for the water. If you size those two components correctly, you will need nothing else.

 

[karimwassef]

True but the purpose of the air cooling coils, etc... is to reduce my electric bill without severely handicapping my upfront capital expense. I'm looking for the lowest total cost solution that is tolerable.

I may need an HVAC but I would want as much passive cooling as possible to minimize the cooling electricity requirements.

I could spend $50k on a photovoltaic solar panel-converter-battery system that runs a $10k DC compressor AC... I wouldn't have to pay much for electricity and would be self sustaining... but my entire system budget is $50k... so can't afford it.... off grid is expensive.