Cool storage time of phase change wallboard room in summer

More and more attention was paid to phase change energy storage in air conditioning domain and construction energy conservation,and became the focus of the international research. Through the test and analysis of the parameters of the indoor thermal property in phase change wallboard room and ordinary room,the effects of using phase change wallboards on indoor temperature in summer and air conditioning are obtained. The combination of construct enclosure and phase change materials can stabilize indoor temperature,improve indoor thermal comfort,reduce the frequency of the operation of air conditioning facility,cut the initial investment and operation expense,and meanwhile play an practical role in "the power balancing between the peak period and the valley period" policy. Through the experiment and the test of the effects exerted by phase change wallboard room and ordinary room on the indoor thermal environment,it is obtained that the phase change wallboard can reduce the fluctuation range of indoor temperature and the heat flow from the outside into indoor environment in summer. According to the study,it is found that the effect of cool-storing for 5 h is obvious. Through the analysis of the phase change wallboard without air conditioning in daytime,it is obtained that the frequency of the operation of air conditioning in phase change wallboard room is smaller than that in the ordinary room,which can prolong the lifetime of the facility and reduce operation expense.

Room temperature and humidity decoupling control of common variable air volume air-conditioning system based on bilinear characteristics

Variable air volume(VAV)air-conditioning(AC)systems are widely employed to achieve a comfortable room thermal and humid environment depending on its better regulation performance and energy efficiency.In the single coil VAV AC system,conventional proportional-integral(PI)control algorithm is usually adopted to track the set-points of the room temperature and humidity by regulating the supply air flow rate and the chilled water flow rate,respectively.However,the control performance is usually not good due to the high coupling of the heat and mass transfer in the air-handling unit(AHU).A model-based control method is developed to realize the decoupling control of the room temperature and humidity according to the bilinear characteristics of the temperature and humidity variation.In this control method,a bilinear room temperature controller is used to track the room temperature set-point based on the real-time cooling load,while a room humidity controller is used to track the room humidity set-point depending on the real-time humidity load.The control performance was validated in a simulated VAV AC system.The test results show that comparing with the conventional PI control,the room temperature and humidity are controlled much more robustly and accurately by using the proposed model-based control method.

A new research of identification strategy based on particle swarm optimization and least square

Within the heat and moisture system that is complex in the air-conditioning rooms of large space building,the existence of delay makes the stability cushion reduced,which thereby makes the estimated parameters more complex.In this paper,particle swarm optimization(PSO)is integrated with least square(LS)to improve least squares(short for PSOLS).LS,optimized by PSO,identifies the heat and moisture system parameters of the existence of delay in the air-conditioning rooms by sampling input and output data.In view of this delay system,the identification is an effective solution to nonlinear system which LS can not identify directly.The simulation results show that PSOLS is quite effective,and its global optimization has great potential.

Finite time thermodynamic analysis and optimization of water cooled multi-spilit heat pipe system(MSHPS)

This study focuses on the heat transfer characteristics of the evaporation terminal,the cool distribute unit(CDU)and refrigerant flow distribution of a water cooled multi-spilit heat pipe system(MSHPS)used in data center.The finite time thermodynamic analysis,the exergy method and the software SIMULINK was employed to build the simulation model of the combined system.The results show that the IT servers should concentrate on arranging at the location below 1.3 m.The CDU has a heat transfer of about 74 J in a period of 6 s.And the optimum flow rate of the CDU is 0.82 kg/s.The flow distribution characteristic of a CDU which connect 2 heat pipe evaporator terminals of 6 kW was calculated,and the working fluid is R22.Then the free cooling time,part time free cooling and energy saving potential in major cities of China were analysised.The energy saving potential is from 61%to 25%.The results are of great significance for the operational control and practical application of a MSHPS and other pipe-net systems.