Principles of energy efficient ammonia refrigeration systems

Ammonia refrigeration systems are typically large energy users and hence good targets for energy efficiency improvements. Common opportunities to reduce energy use and improve energy efficiency include reducing refrigeration load, increasing suction pressure, employing dual suction, decreasing minimum head pressure setpoint, increasing evaporative condenser effectiveness, and reclaiming heat. Estimating savings from these measures is often difficult because of the complexity of the equipment and controls. However, the fundamental energy response of ammonia refrigeration systems to these measures can be estimated using a simplified model. An understanding of these responses is often an important first step to designing or optimizing the performance of actual systems. Thus, this paper develops a simplified model for simulating a single-stage ammonia refrigeration system and uses the model to estimate how energy use changes in response to the opportunities mentioned above. The results show how system energy use and potential energy savings vary with ambient wet-bulb temperature. The results give designers and operators insight into possible savings opportunities.