We once assembled an incubator for a client using an old refrigerator. We removed the compressor and evaporator and installed a vortex cooler. It runs off compressed air and can circulate the air in the "incubator" without the need for a fan. The refrigerator was an old unit they took from their canteen kitchen so all they bought was the vortex cooler.

Vulcan has a good idea started there. Your answers are actually all available. You didn't say what you were incubating.

If you did re-assemble a refrigerator's components, I trust you'll know enough to not let the refrigeration parts get contaminated with moisture or air AND that you would NOT change anything about the lengths of any coils or tubing, they are critically designed for performance.

Your incubator box has a "load" itself, (how tight it is and how well insulated ) then there is the load of what is growing in it...does it need fresh air to breathe? Is so, that fresh air is "load" as well. The FUNDAMENTALS OF REFRIGERATION handbook lists loads for a variety of things.

Offer some more details and we'll help you out.

I am incubating eggs, in an insulated enclosure.

The machine will run at fairly steady state conditions, what I am trying to do is control a change in temperature of less than 0.5 deg C.

Most incubators use a heating element to raise temperature when needed but then rely on fresh air to drop temperature, the problem is that it does not remove the heat quick enough and also upsets the humidity ratio.

Oh man!

Incubating eggs! So you need heat instead of cold but why go with refrigeration units?

I visited a chicken farm once and they used low wattage bulbs with dimmers for temperature control. Fans provided ventilation. I don't think they were much concerned with humidity since the place was uncomfortable (for me at least). Conditions may be different for your place, however.

A system like that should be easy enough to automate.

Perhaps the heat extracted by refigeration is to be used for incubating...?

Any good literature on refrigeration should give you the quantity of heat extracted and from there you can work out the heating temp you should achieve if you know your refrigerant, the volume to heat, insulation type, ambient or outside temp etc.....

I'm still not sure why you want a refrigeration system. Will you ever have a need for cooling, either to lower the temperature or lower the humidity? If not, then I would think electric resistance heating would be the way to go.

If you recirculate the air and your box is insulated, then it should be fairly easy to control the temperature. What am I missing??

The incubator we assembled was a "cooling" incubator, used in a pharmaceutical manufacturer's laboratory. They put cultures in petri dishes inside (I didn't ask what was in them ) and stored them at 24 +/-0.5°C. They added a temperature recorder later and informed us that the whole thing worked pretty well.

The ref only provided an insulated cabinet. All the working parts were removed (compressor, evaporator, tubes, etc.). Since the vortex cooler kept injecting air, a vent was required so as not to pressurize the cabinet. The hole provided by removing the tubing was conveniently used.

Hi there, I do not know the size of incubator that you are dealing with, but here are some suggestions from my experience as a heating cooling contractor.

1) I have a client who has made a beer brewing incubator which he keeps at 24deg Celsius by thermostatically controlling /stepping his heating equipment ( a series of incandescant bulbs. Cooling is then by fan forced ventilation. unit size is about 600mm high 450mm wide and 450mm deep. 3 bulbs 60 watts, 75 watts 100watts.

2) An electrician contractor friend makes piglet heaters by using reflective bulbs, controller is an electronic thermostatic controller which is the only way to get the close control that you are talking about.

3) We also build Pig Semen storage fridges and Cold rooms. 125 litre fridges with standard refrigeration equipment with the addition of a 25 watt bar element and circulation fan, All controlled by an electronic controller. The electronic controller has a alarm output which is used to switch the heater if the temperature goes to low. This system is very effective and keeps a very stable temperature environment. The cold rooms operate on the same principal just a little larger. preprogrammed dead bands and delays prevent rapid cycling. Operation temperature is 17deg. C.

Hot water can also be used. Regards Cobenster @ Gmail.com

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Most the incubator I have seen where on my Grandmothers farm. My uncles raised game birds like pheasants and quail. It was just a wood box with drawers. Used a light bulb for heat. Had a fan that pulled air through. You controlled the temperature by opening or closing a vent into the box. Humidity level was controlled by cup with felt in it under the lamp. A water bottle with with a valve would control drops of water onto the felt. My uncles had made them. They seem to work well. You could use a bi-metallic strip to mechanically control the opening and closing of the vent to regulate temperature.

What is the temperature that you wish to maintain?

What is the product intended to incubate? Quantity?

The answers to all questions are germane to the heating/cooling loads.

To answers a few questions about why I need cooling.

I am incubating chicken eggs, chicken eggs are incubated for 21 days. During the first part of the incubation process heat needs to be put into the incubator for the embryonic process to start.

As the embryonic process continues the eggs start producing their own heat and so by the later stages you need to start cooling the air otherwise you would have well cooked eggs.

The set point temperature is around 37 deg C. So to maintain this temperature you need to be constantly removing or adding heat depending upon how long the eggs have been incubating.

I am looking to build a machine to carry around 1000 eggs, a 1000 eggs produces around 250 Watts of heat.

I'm not very knowledgeable with refrigeration circuits but there are lots of books in local bookstores (I took a browse in one yesterday). I can, however, recommend vortex tubes because of their simplicity and selection is easy by going to their wedsite. There was a recent thread on them and I gave a few manufacturers in case you're interested.

http://cr4.globalspec.com/comment/126647/Re-vortex-tubes

I didn't know that eggs produce their own heat in the later stages. I learned something new today.

Thanks for the additional info. I'm sure we are getting closer to a solution! I still think that a refrigeration system is not needed.

What is your highest ambient temperature during incubation? Is is cool enough where you can introduce outside air to the recirculated air to accomplish the cooling? If not you may want to add a small air to water coil to cool the air enough for the few times that you will need it.

Previously you had mentioned concerns abouit humidity. How important is that?

How interesting.

As a boy circa 1930 I visited a small town, central US, in the early spring for several years. There was a large local hatchery providing baby chicks for the farmers for miles around. They had NO refrigeration.

Circa 1960 my daughter (and I) made an incubator for school science class using a wooden box, glass window, and a low wattage light bulb for heat. Adjusted temperature by and adjustable opening to allow the flow of room air through the box as needed. The air cooling was to compensate for the excess heat from the lamp, not from the eggs.

I found that chicken eggs must be kept at 100 deg.F (99) for some other species.

CARE AND INCUBATION OF HATCHING EGGS

Others have indicated skepticism as to the need for a refrigeration unit as other simpler and less expensive/complicated solutions are available. i.e. an evaporative cooler on an incoming circulation air stream. I doubt that refrigeration would be required anywhere except in HOT climates. The link may provide other helpful information for you operation. SS

All the new single stage incubators that have come onto the market have cooling.

What we are trying to achieve is a steady temperature with minimum overshoot and undershoot on temperature.

At the same time humidity and CO2 levels are also important. Therefore cooling with new air also affects the above parameters. So by using heating and cooling you can control air temp without affecting air quality.

My brother,

Then why did you start in the totally reverse direction of refrigeration when all you were looking for is heating for incubation.........? Beats me, I confess.