| 摘要 |
<p>In prior hot gas defrost systems for refrigeration systems part of the hot gas is diverted to flow through the cooling coil (34a, 34b), while the remainder flows through the condenser (16) to avoid overload of the compressor (10); as the ambient temperature decreases the compressor output pressure also decreases, decreasing the amount of hot gas available so that the defrost period also varies. It is therefore necessary either to adjust the length of the defrost period, or make the period sufficiently long to ensure defrost at all times, the latter resulting in inefficient operation. With the present invention, during a defrost period, upon detection (107) of a lower pressure at the condenser outlet (20), a valve (108) at the compressor outlet bypasses the condenser (16) and delivers hot refrigerant directly to the liquid collector (22), or to the liquid line functioning as a liquid collector, a check valve (116) preventing delivery of refrigerant to the condenser (16) and return of refrigerant from the collector (22) to the condenser (16). If the pressure reaches a higher value indicatingthat the compressor (10) is overloaded, the valve (108) returns to delivering the refrigerant to the condenser (16) until the pressure drops again to the lower value. Alternatively the valve (108) progressively bypasses the condenser (16) to the collector (22) to maintain a smaller range of pressure variation.</p> |
