23 September 2011

QUICK SELECTION OF HEAT PUMP TYPES AND OPTIMIZATION OF LOSS MECHANISMS


Making a rough estimation of performance for conventional vapor compression
and vapor recompression heat pumps is straight forward: Dividing the Carnot efficiency by 2
results in a reasonable estimate. Still, actual performance of actual heat pumps could easily
vary to a large extent.
With new and innovative heat pumps the discrepancies between the rough estimate and
actual performance might be even larger as the Carnot efficiency is not the upper limit
anymore due to the use of temperature glides. Lack of a simple method to determine the
approximate performance of a heat pump will hinder the implementation of these novel types
in process industry.
In this research it is shown that, for mechanical heat pumps, making use of the available
temperature glide increases performance and reduces the payback period. While at low
glides, heat driven absorption heat pumps show better pay back times, mechanical heat
pumps with large glides show to be more effective even at high temperature lifts. Due to
better performance, mechanical heat pumps are able to achieve better economical results
over their technical life time although they can have a longer payback period.