Description

Historically, heat pumps have suffered from three major deficiencies; limited heating capacity in colder climates, generally low seasonal performance factors, and poor reliability. Many adva~ ces have been made since heat pumps first appeared commercially in the 1950s, but there are stlll numerous opportunities for improvement. Usual approaches to improving heat pump performance in the past have centereo upon the following: 5

1. Improved utilization of heat exchanger surface such as flooded evaporators and liquid free condensers.
2. Larger heat exchanger areas for a given size unit.
3. Improved controls; such as defrost timers, pressure and temperature limit controls and others.
4. Improved compressor design, with more efficient motors and valves, better internal flow paths, and improved oil circulation control.
5. Improved auxiliary heating, using better coordination of building sensible heat storage and heating demands, or fossil fuel supplementary heat. Newer methods of achieving better performance and reliability are becomming economically feasible as energy prices rise.

Some of the new approaches are:

1. Solar-assisted heat pumps
2. Thermal-storage heat pumps
3. Multiple-heat-exchanger and/or multiple-compressor heat pumps
4. Staged-compression heat pumps
5. Flow-modulated (capacity-controlled) heat pumps
6. Combinations of the above,

All of the preceeding new concepts hold great promise, and each should be examined thoroughly to show which concept or combinations of concepts are best. The flow-modulated or capacity controlled heat pump concept requires the least drastic changes in system design, and has therefore been chosen for further study in the present work.

Citation: ASHRAE Transactions, Volume 83, Part 2, Halifax, NS

Product Details

Published:

1977

Number of Pages:

21

File Size:

1 file , 1.4 MB

Product Code(s):

D-HA-2461