DIY Chiller With Titanium Heat Exchanger

[weisoon]

I am think of DIY a commercial type of chiller for my new tank using a Titanium heat exchanger. Need the help of air condition expert's opinion on the various parts need to make the chiller work. Basically, the system will be remote condenser type where most of the system will be situated outside the house and only the Titanium heat exchanger will be located under the tank. As such, there will a long run of refrigerant for the system to run from the outside to the tank.

Thinking of using the normal single split compressor unit used for cooling room. However, need expert's advice on the following questions:

1. These single split compressor, do they have the receiver/dryer, expansion valve and the low pressure safety switch inside the unit? Last heard from some people that the unit do not have all these.

2. For long run of refrigerant, is there a need for a solenoid switch to maintain the pressure of the refrigerent in the line from the compressor to the expansion valve when the compressor is off? Heard again that if there no solenoid switch, the return line from the Titanium heat exchanger to the compressor will have some negative effects.

Here's a diagram, but it may not represent 100% as some of the components discussed above is not present.

[weisoon]

Anyone??

[piglet]

I have a relative who operate a electrical and aircondition company. He is also the service company for LG air-condition. Been in market for over 15 years.

[lightningstrike]

if u r not in 2 much of a hurry for this DIY chiller project, maybe i can help u with my so called "expertise" in a/c in december when i come back from japan. i m quite interested in developing 1 too. but i'll hv to warn u, i know nuts abt the electrical/electronics aspects.

[weisoon]

Lightningstrike thanks for the offer. Piglet, will PM you soon to get the contact of the shop, just to ask them some questions.

Already know a bit on the topic of HVAC( Heating, Ventilation, Air-Conditioning). Basically, its just that want to know more about the 'contents' of the normal single split unit before deciding on whether to use a single split or just a commercial refrigeration unit (can see form some hawker stall's chiller/fridge). Price wise, both quite the same except that the split unit looks neater that's all.

Basically, from what I have shown in the diagram, the needed components are:

1. Compressor

2. Condenser

3. Receiver/Dryer

4. Balanced port TEV(Expansion Valve)

5. Ti heat exchanger

6. Low pressure cutout switch

7. Solenoid switch (optional but good to have it installed)

Main problem here is I think is whether the local air con man has the better equipment to do the measuring and charging. One needs a good electronic integrated pressure meter to get the 'super heat' figure correct else there will be problems in the long run, especially to the compressor and of course waste of power to run the unit in-effeciently. Also need to know if a superheat figure of 10 degree F is adequate enough.

The heat exchanger I am getting is for cold water application compared to those for warm water application. Cold water rating means down to 2 or 3 degrees C and warm water is for upto about 25 -26 degrees C. Overkill a bit but may as well go for the better unit. Estimated length for 3/4 HP of the Ti coil at 1/2 diameter is about 15'. Unit is made in Canada whereas the local unit has the most about 4' run of the Ti coil in the shell and the look of the material is quite questionable ( meaning colour of their so called Ti) although the price is very cheap. Price difference is about 3-4 times.

[lightningstrike]

hi weisoon, u'll be surprised to know that i m working on a HVAC project for an automobile in japan now.

[weisoon]

lightningstrike

Guess the principles of auto heating and air conditioning is pretty much the same as that for a reef tank except in Singapore, the heating part will not be required.

Just as a matter of interest, does the car's aircon needs adjustment to the superheat figure? Or is it just plug and charge up?

I will be very interested to know.

[lightningstrike]

well, in a/c principles r pretty much the same whether it is for the automobile, commercial, industrial or domestic entities. but as for chillers, i think a cooling core is used. superheat for car a/c system is based on calculations and deriviations from testing. charging amt for refrigerant, e.g. R134a is based on performance subjected to a hot room test.

[weisoon]

well, in a/c principles r pretty much the same whether it is for the automobile, commercial, industrial or domestic entities. but as for chillers, i think a cooling core is used. superheat for car a/c system is based on calculations and deriviations from testing. charging amt for refrigerant, e.g. R134a is based on performance subjected to a hot room test.

My guess for you mentioning 'a cooling core is used' = heat exchanger = evaporator?

My guess also is that the TEV that the car uses is the non adjustable type as there are in the market fixed as well as adjustable TEV that gives a specific amount of superheat.

Well, most of commercial refrigerant used are the R22 or R12.

[lightningstrike]

for industrial, commercial and domestic a/c...... yes R22 is the common one....... but for cars....... R134a. TEV??? this sounds foreign to me...... do u mean TXV??? a.k.a expansion valve?

really so sorry for getting so here.

[weisoon]

Yes, talking about the same thing. TEV=TXV=expansion valve depends on which manufacturer.

[weisoon]

So, for cars, do they fix the superheat at 10 degrees F?? Any way to find out? Also do they incorporate an low pressure cut out switch?

[lightningstrike]

to be frank, i m not very certain as to what is the exact value for superheat, it varies from car to car, system to system. and yes a pressure cut off switch is incorporated to the comp.

[weisoon]

Hope you can help check it out if the superheat values same or not the same for most cars.

Again, my guess is that most air con systems will need about superheat of average value 10 degrees F. Range can be of course between 6 - 12 degrees F. However, I may be wrong.

On the other hand, will check further from some air con experts.

[weisoon]

So far, we have been discussing about superheat which is no doubt an important factor when charging the system to work properly. The other important factor to look at is the subcooling.

Subcooling will be needed to be measured when used with systems with TXV installed. The sub cooling range will be in the bracket of 12-15 degrees F for optimum operation of the system.

The co-relation between superheat and subcooling is: sub cooling will need to be at least 3 degrees F higher than super heat.

SC=SubCooling

SH=superHeat

SC High=Condenser coil holding too much liquid results in compressor working harder

SC Low= Exit from condenser still contains gas and entry to the TXV and reduce the system's ability to cool.

SH High= Liquid in the evaporater turns into gas too fast and result in not maximizing the use of the coil.

SH Low= Liquid has no chance to absorb heat and turn into gas and results in liquid returning to the compressor causing damage.

So, measuring /adjusting the subcooling is required in system with TXV(preferred adjustable unit) installed and followed by a cross check of the superheat to be in the correct range. With both in order, then the system will be working in optimum condition.

[alvy]

http://www.aquarealms.com/forum/viewtopic.php?t=12391

[lightningstrike]

as for charging amt, the normal way to do it is to gauge from the sight glass. gauge line is where the bubbles juz abt clear in the sight glass.

hi alvy, thxs for the valuable info.

[alvy]

note: charge only when chiller is running with full load..

i did not install the sight device, i measure the superheat value for gauging the charge.

[weisoon]

alvy

Thanks for the article. Some issues on your article if you can shed some light....

1. Did you have an low pressure cutout switch installed?

2. Spoke to an technician, he was talking about installing an solenoid valve after the condenser so that when he compressor is cut out, the liquid line on the high pressure side can be 'locked' in place. He added that was because of the long run of the refrigerant from the outside of house to the heat exchanger. This is something quite new to me and still trying to understand what he was trying to say. I thought that once the compressor is cut out, the line either the high or low pressure side will remain in the line anyway and wonder what the solenoid can help to do. Have any idea?

3. Was thinking of using the IKS temp probe with the IKS Aquastar to act as the temp controller. The problem is that the hole fitting at the heat exchanger may not fit my probe. The IKS probe is silicone coated and this is good for reef application but wonder the ones on the market like Johnson Controls has one that is coated instead of just a metal body. Can share which brand you using?

4. The superheat and the subcooling values for your system is at 10 degrees F and 13 degrees F respectively?

Lightningstrike

Guess the sight glass may not be availabe as some receiver/dryer on commercial units does not have one installed as compared to cars.

[alvy]

I do not know the rational of retaining the high pressure on the wet end....it might have something to do with the restart cycle of the compressor using a TEV. after the compressor shuts off, it may not be able to restart immediately due to lockup in the compressor. something to do with pressure equilisation across the high pressure and low pressure end..this is from my own observation of my own diy chiller..after shutoff the system need to stay off for a few mins in order to restart again (say after a momentary power trip)... maybe the solenoid valve have something to do with this issue...for my case, i simply set an anti-restart duration within my temp controller so tt the system do not switch itself on instaneously when power is up.

i do not know wat brand my probe is, but i simply chuck it into my sump..it is stainless steel made but it can rust..after ard 1 yr of usage..it will screw up..so i replace the probe with another one $15..i dun want to silicone it becoz it might lag the temp response.

I totally forgot about the super heat theory liao..but i remember reading a lot about it before i charge the system and i ensure the values of my system fall within the optimum range....i have no doubt of the way of charging since my system has been efficient since day 1..

[weisoon]

Thanks for your input alvy

I thought the Ti heat exchanger has 3 fittings other than the 2 for the water flow in and flow out. They are the refrigerant in, refrigerant out and the last is a fitting for putting in a probe to be connected to a temperature controller. Just want to confirm that you did not put the probe into the fitting and instead you just put the probe into the sump to control the temperature?

You obtained your heat exchanger locally?

[lightningstrike]

if the sight glass is not available, then juz hv to make do with the manifold gauge for the charging amount. what alvy stated is correct. charge only when chiller is running with full load.

[weisoon]

Agreed with alvy and lightningstrike.

Some people even recommend charging it by simulating uncommon heat spell by covering up the condenser with cloth/plastic. In this way, the worst senario will be meet in the event of high ambient temperature increase.

This way will also be good if after some time of usage, the condenser will be filled with dust and its heat dissipating capacity will be reduced. This condition will be similiar to unusual heat spell.