Water Heat Pump Air-conditioning Of Ship Based On PLC Control System

This article analyses and discusses the working principle of the water-heat pump system of ship, and the designing method of PLC control system.Based on reverse Carnot cycle, water-heat pump absorbs heat from cryogenic heat source, and sends it to high-temperature source by using electric energy. The quantity of heat sent to high-temperature heat source is not only larger than the consumed heat, but also larger than that absorbed from cryogenic heat source, thus reaching the aim of saving energy.Compressors belong to load of pump. Our analysis shows that when we change the valve opening of cycling system without changing the rotational speed of the compressors, the consumption of heat is very high. On the contrary, when we change the rotational speed of the compressors, while the valve opening of cycling system remains unchanged, the consumption of heat is very low. This is an effective way of saving energy.When the devices of speed control by frequency variation are used, due to the effect of the electric capacity of filter inside the frequency transformer, cosφ≈1, therefore, the reactive power loss is greatly reduced, while the active power of electric network is greatly increased.With the application of energy saving devices by frequency variation, the starting electric current begins from zero by using the soft starting function of frequency transformer, with its maximum value not exceeding the rated current, thus reducing the impact on the electric network and the demand for electric supply capacity, as well as the energy loss caused by the frequent start of the electric motor of the compressor.This article introduces the diagrammatic layout of PLC control system, the working principle of frequency transformer and its usage, the construction of mathematic modeling of heat pump of ship and its replication method.The result shows that by adopting the design introduced above, water-heat pump air-conditioning of ship helps to get the energy efficiency ration 3.0-5.7. It is better to be used on large ships with capacity of more than one thousand tons or ships with deep load line. Compared with air-pump air-conditioning with the energy efficiency ration of about 2.2-3.8, it can save energy 30-40 %.