Research On Diffusion Of Refrigerant Leakage In Ammonia Refrigeration System In Limited Space

Ammonia refrigerant has many advantages such as high refrigeration efficiency and large energy efficiency coefficient.Under the background of global promotion of green and sustainable development,ammonia refrigerant is widely used in the refrigeration industry due to its natural environmental protection and pollution-free characteristics.However,the ammonia refrigerant is flammable,explosive,and toxic,and is included in the list of hazardous chemicals.In recent years,ammonia leakage accidents have occurred from time to time,causing casualties and property losses.Aiming at the situation of ammonia leakage in the refrigeration system,this paper uses a combination of experimental research and numerical simulation to study the diffusion process of ammonia refrigerant leakage in the limited space of the refrigerating machine room.A calculation model of ammonia leakage and diffusion in a limited space is established to simulate the leakage process of the ammonia refrigeration system.At the same time,the specific refrigerating room is used to conduct ammonia leakage and diffusion experiments to verify the accuracy of the simulation.Through simulation and experiment,the laws of diffusion of ammonia leakage under different working conditions are obtained,and the time to reach a certain concentration is inferred,so that when an uncontrollable ammonia leakage accident occurs in the refrigerating room,it can provide a reference escape time for the operators.It also provides a suitable installation location for the ammonia leakage alarm sensor.By studying the leakage and diffusion process of ammonia refrigerant refrigeration system in limited space,the following conclusions are drawn:(1)When the door or window of the refrigerating machine room is opened,the ammonia concentration near the door or window is reduced,and the risk is lower;(2)When the accident fan is working,the ammonia concentration at the inlet of the accident fan increases,and the ammonia concentration in the lower part of the space decreases,which is beneficial for the operators to escape;(3)When designing the refrigerating machine room,it is recommended to install two doors on two adjacent walls and keep a certain distance.The accident fan should be placed near the equipments with a large amount of ammonia which should be placed near the wall;(4)When the pressure in the ammonia storage container increases,the kinetic energy of ammonia leakage increases,and the concentration of ammonia gas increases rapidly.The escape time of the operators decreases with the increase in the pressure of the ammonia storage container.The escape time is the shortest under high pressure,medium and low pressure is similar,and medium pressure is slightly less than low pressure,and the risk factor is higher when the ammonia leakage accident of the high pressure storage container occurs;(5)The ammonia leakage alarm sensor should be installed on the roof of the machine room directly above the equipment with a large amount of ammonia or at the intersection of the roof and the vertical wall.It is not recommended to install it directly above the door of the machine room.The installation height of the ammonia leakage alarm sensor is directly proportional to the time from the occurrence of ammonia leakage to the automatic start of the accident fan.Based on the above conclusions,although ammonia is a dangerous chemical,as the refrigerant of the refrigeration system,ammonia is a natural and environmentally friendly refrigerant.Under normal working conditions,it is impossible to instantaneously cause uncontrollable ammonia leakage,which can ensure that operators have time for safe evacuation from dangerous places.The paper can provide valuable suggestions for safety assessment.