Heat Pumps and Cooling Towers

Would you be surprised to hear that a cooling tower is a type of heat pump. (Ok, maybe a bad stretch of a term. )

But I believe you'll find that the problem typically comes down to an economy of scale. Specifically the amount of heat transfer of a cooling tower would likely overwhelm the capacity of a heat pump. The predominant method a cooling tower removes this large amount of heat to be dissipated as latent heat, the transfer of water from liquid to a gas. This is not to say that a co-generation approach of steering heat from waste to useful cannot be done depending on the application. But I suspect that concentrating the heat with a heat pump to a higher temperature will only rarely be beneficial.

My thinking was along similar lines. It seems that to utilize the heat a typical cooling tower dissipates a very large heat exchanger would be needed, Increasing this would require larger circulation pumps and on and on and it seems that the overhead cost and maintenance of the heat-pumps would offset any beneficial savings from the heat pump installation.

Of course that is a purely economical view of the situation, for a situation where carbon-footprints and environmental impact have greater value perhaps a system set up to reduce waste heat would validate these costs.

-T

Yes, ongoing maintenance costs for such a huge system would be an Achilles heel, let along the initial capital outlay. It's just when one looks at the size of those cooling towers it seems incredible that a better solution (apart from where co-gen or local heat is practical) doesn't come forward.

redfred sounds informed, and my free-lunch-o-meter hasn't returned a legitimate blip in years. But I'd love to see some numbers...

RR

I too would like to see the figures.

Although I understand the principles of heat pumps, I am not as sure how I could go about calculating the necessary elements in such a system. If someone will give me pointers I'm willing to ave a go though.

I think it would depend in what nearby energy-using processes can benefit from having a higher-temperature source available. One example is hot-gas defrosting in refrigeration systems. Low discharge pressures are desirable for energy savings in the overall system, but they might not produce enough volume and temperature of hot gas for effective defrosting. But using a heat pump (compressor) to raise a fraction of the discharge stream to a useful temperature, the bulk of the discharge can remain at lower pressure/temperature.

One must assess on a case-by-case basis the energy balances involved, the pressure/temperature differences that drive the process, and the costs of equipment. Some schemes will be viable; others not. The concept is definitely valid in the right circumstances.

Its too bad industries couldn't work closer together. One factories waste heat is just enough to supply heat for another factories needs.

I am a big fan of conservation of energy. I always wondered why you used to see that flame burning on top of a stack at a refinery. I realize that it is burning vented fumes to prevent explosions, but couldn't you put a boiler on top of that flame and make electricity? There has to be other applications where one could conserve the energy from cooling in many of the metal fabrication factories.

Drew

Replies appear based on the premise of returning Steam to Water.

Steam and Carbon Dioxide are both gas reducable to liquid.

Cooling towers are usualy associated with Steam and its high heat need.

Low heat need of Carbon Dioxide makes use of the heat pump.

Excuse my ignorance. Are you saying a high-pressure CO2 circuit running through a turbine could add a further power stage?

Thanks.

A heat pump itself consumes energy. Typically a one KW pump can pump about three times heat. But the over all efficiency of the thermal plant is about 33%. So what you gain by pumping is lost int he generation with the added nuisance of an active additional system to be maintained.