Study On Variable Load Ratio Characteristic Of Multi-connected Air-condition System And The Indoor Fluid Field In Heating Mode

Energy issues are concerned because of the global financial crisis,energy-saving and emission reduction policies are implemented with great efforts in China at present, Conservation and efficient use of energy is of great urgency.In resent years, multi-connected air-condition systems are applied widely for its good part-load performance,high-SEER,thermal comfort,etc.However the studies on variable load ratio characteristic of multi-connected air-condition systems are far from satisfaction, while it has important significance on practical engineering design to do this work.The operation of multi-connected air-condition systems are very complicated,and the refrigerant tubes' length could directly have influence on their refrigerating and heating performance.The MDV system K-1 used in School of Environmental & Municipal Engineering building of Xi'an University of Architecture & Technology was tested,and the temperature change curves along the refrigerant vapor pipe in winter were carried out.The relationships of the refrigerant steam temperature change with the length etc.were analyzed and the specific methods to reduce the temperature damping were proposed,which supplied theoretic foundations for the multi-connected air-condition system designing.The temperature time-varying curves of the refrigerant in and out of every indoor unit were also tested under different load ratios,and the variable load ratio characteristic of the system was analyzed from the test.According to the result,designing good control strategy was considered as necessary condition to improve the performance of the systems and the comfort ability of the room.Based on the test result,theoretical arithmetic for performance coefficient EER of the system with different load in heating mode was done and the relation between EER and load ratio was achieved.The result shows that the performance coefficient EER of the system when the load ratio is from 50%to 70%is higher than EER with other load ratios.The temperature distributions of an office in Xian with radiator heating and VRV air conditioning modes were measured respectively by IMP.The numerical simulations were also carried out for the above two space heating modes.Mathematic modes were established according to the office and the indoor temperature field and velocity field of two heating modes were simulated.The value of temperature gradient is about 3℃in VRV air conditioning mode but 0.7℃in radiator mode was showed in the results.The two mathematic modes are appropriate because the numerical simulation result is identical basically compared with the measuring result.The temperature field and the velocity field of the radiator heating mode was considered better in uniformity than the VRV air conditioning mode.