HO-82-05-4 -- The Steam Ejector as an Industrial Heat Pump PDF

Industrial heat pumps are used in nonresidential, noncommercial applications to upgrade lowtemperature heat sources to more useful levels. Typically, low-grade process steam is produced from a warm water reject stream, although there are many potential combinations of heat sources and end uses. A heat pump is of interest in upgrading industrial heat because of its COP - coefficient of performance - which is defined as the ratio of the heat delivered (or removed) to the energy required to effect the desired heat transfer. This ratio, the COP, is greater than unity for temperature boosting, meaning that for every joule of energy required to transfer heat to a higher temperature, more than one joule of heat can be transferred. For the typical mechanical vapor compressor heat pump producing steam of atmospheric or greater pressure, a COP of approximately 3 to 4 may be expected.

In this paper, the steam ejector is analyzed for use in industrial heat recovery applications and compared to mechanical compressor heat pumps. It should be noted, however, that these analyses are not case histories but are best estimates of expected performance based on extensive surveys of manufacturers' data and the available literature on ejector performance.