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funkybrown
04-01-2012, 09:51 AM
Hello,

Firstly i would like to say that i am not a refrigeration engineer, and that I only understanding the basic principles of refrigeration, so please be kind with your comments. I appreciate this may be in the wrong area of the forums, or should not be here all together, but i would like to know if possible...

Could you use a refrigeration loop to be used as a forced are heater?

For example, i would like to have a compressor with the inlet open to atmosphere, this may require a pump? Instead of cooling the condenser, I would like to apply a gentle heat while hoping to reach 3-4Bar pressure and maintaining an ambient temperature or higher. I would then look to apply 1000W for example onto the evaporator so that as the pressurized air expands, it draws the heat out before using the suction line as an exhaust giving me a nice warming flow of air.

Thank you in advance for your comments.

The Viking
04-01-2012, 08:06 PM
I don't know what you want to achieve with such a system...
You would end up with an efficiency below 1, in our game we aim for at least 5.

Is there a reason for the 3-4 Bar of air pressure?
Otherwise we would use what is commonly known as a fan heater, you can pick a 2.2kW one of those for about a tenner at any DIY shop and most supermarkets...

chemi-cool
04-01-2012, 08:36 PM
Sounds like you have never heard of a small ac unit in heat mode.

MikeHolm
05-01-2012, 12:55 AM
Look at almost every heat pump available in North America. They use refrigerant to heat air.

BTW, much better to heat water in the floor.

The Viking
05-01-2012, 01:55 AM
Look at almost every heat pump available in North America. They use refrigerant to heat air.

Ah,
But there is an important difference there. The air to air heat pump, as well as air to water and all other types of heat pumps commercially available, are recirculating refrigerant...
The system in the OP's example is utilising free flowing compressed air that then are heated by an electrical heater.

Don't get me wrong, proper heat pumps are great and I am a firm believer in them and Im still trying to figure out what the OP actually trying to achieve, hopefully he will get back on and tell us.

MikeHolm
05-01-2012, 02:00 AM
Ah,
But there is an important difference there. The air to air heat pump, as well as air to water and all other types of heat pumps commercially available, are recirculating refrigerant...
The system in the OP's example is utilising free flowing compressed air that then are heated by an electrical heater.

Don't get me wrong, proper heat pumps are great and I am a firm believer in them and Im still trying to figure out what the OP actually trying to achieve, hopefully he will get back on and tell us.

Me too.......

funkybrown
06-01-2012, 02:17 PM
Thank you all for your comments.

This is a concept for a forced air heater to be used in hazardous environments. There are temperature limitations and all electrical terminations require certain degrees of protection.

There are already hazardous fan heaters available but due to the approvals, they all command a premium. A 2.2kW fan heater was mentioned for a tenner... a hazardous area version would be in the region of 3000-4000.

The initial thoughts were loosely based on Dyson's bladeless fans using 'air multiplier technology'. Due to the patents they will hold for this, I was looking at using a compresser / pump combination instead of their integral fan. If we can stay away from fans, there are a lot less hoops to jump through when certifying the product.

The 3-4Bar pressure was to allow the decompression at the evaporator to 'absorb' the heat and eject heated air through an exhaust. This can be increased pr decreased to achieve the results required. I do not want a closed loop as this would defy the concept, and create more of a heat exchanger increasing cost.

I am intending this to be a portable unit to be used as a solution for small and medium space heating on oil platforms, and chemical plants, ammunition stores and flour mills etc.

In short, I want to pump the air from around the unit, through the system, heat it in a chamber, and expel warm air on the other side. We currently sell a fan heater but they are big and bulky. I am looking to reduce size and weight.

If you have any other questions, please do not hesitate to ask.

Thanks again for all your help.

The Viking
06-01-2012, 09:43 PM
I thought there were more to it than the original post gave.
:D

But sorry, I personally can't see it being lighter/cheaper/more portable with a compressor.
(but I have been wring in the past...)

Also, in an explosive environment blowing air through a fridge compressor is probably not a very good idea, at least not in a modern one.
Most refrigeration compressors are using the "intake gas" to cool the electrical motor, your airstream would therefore be in contact with all the bits that potentially generates sparks...

But, not willing to discard the compressor idea all together.
On the sites you are talking about, have they got static air compressors delivering compressed air for tools and the like?
It might be possible to take an air supply from one of those, inject high velocity air in to some sort of venturi nozzle... just a thought.
:cool:

flyinkiwi
06-01-2012, 11:29 PM
It sounds like it would be an easier solution to use heat recovery from the air compressors (if they have them) via a hydronic system - Industrial air compressors reject enormous amounts of heat, and most major air compressor manufacturers offer a heat recovery operation these days.
I have seen compressor rooms reach silly temperatures due to poor ventilation - great for me, easy work resetting air dryer HPs and cleaning condensers... and a fantastic heat source.

Unfortunately, it wouldn't be too portable.

The fan for circulating your air in the conditioned space might be more of an issue if it is a hazardous or explosive environment, but intrisically safe motors will solve that problem.

Stu.

AlexG
07-01-2012, 12:38 PM
Funkybrown,maybe i understood it wrong, but if u have compressed air for free and want to heat it try googling Ranque-Hilsch Effect.
Cheers