Papers by Author: Shun Yu Su

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Authors: Shun Yu Su, Qin Huang, Jian Chen
Abstract: The steady state distributed parameter model of heat exchangers in a heat-pump system was established in this paper. The calculating results of refrigerant quantities in the heat-exchangers show that refrigerant charge quantity in heating operating condition is less than that in refrigeration operating condition. Based on the differences of refrigerant mass flux between refrigeration and heating conditions, the exhaust bypass method to improve the operation efficiency of the heat-pump system was presented. And in order to prevent frosting on the surface of outdoor heat exchanger of the air source heat-pump, the solar energy assisted strategy was also applied in the heat-pump system.
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Authors: Shun Yu Su, Jian Chen
Abstract: Heat conduction in anisotropic materials is quite different from that in isotropic materials. Heat flux vector is commonly not perpendicular to the isothermal surface in anisotropic materials. The advantage and disadvantage of anisotropic materials were analyzed in this paper. The thermal conductivities at one point are not equal in all directions for anisotropic materials. The technique of double skin facade has been successfully applied in many building designs. The application of combining building envelope of anisotropic materials and double skin facade was proposed to avoid its disadvantage. Basing on the combination of anisotropic materials and double skin facade in building envelope, the indoor cooling and heating load decrease in summer and winter respectively. Especially in summer, the effect of energy saving is obvious since the partial magnitude of conductive heat in the envelope made of anisotropic materials could be brought out from the cavity of double skin facade by natural or forced ventilation through it.
1227
Authors: Shun Yu Su, Tian Tian, Jian Chen
Abstract: Calculation of refrigerant quantities in the heat-exchangers of an air-conditioner on refrigeration and heating operating conditions shows that refrigerant charge quantity in heating operating condition is less than that in refrigeration operating condition. The refrigerant control strategies are most important for refrigeration and heat-pump system. Based on the difference of charged refrigerant quantities of the air-conditioning system between refrigeration and heating operating conditions, the exhaust bypass method was presented in order to improve its operation efficiency. This heat-pump system for controlling refrigerant mass flux was analyzed in detail. The results show that the exhaust bypass method has its advantages in controlling refrigerant mass flux for heat-pump system.
3073
Authors: Shun Yu Su, Qin Huang, Jian Chen
Abstract: The magnitudes of heat flux for both isotropic materials and anisotropic materials can be determined from Fourier’s law. But the mechanism of heat transfer in anisotropic materials is quite different from that in isotropic materials. The thermal conductivities at one point are not equal in all directions for anisotropic materials. The magnitude of heat transfer rate of anisotropic material in one direction is not only relevant to the temperature gradient in this direction, but also relevant to the temperature gradient which is normal to the direction. Basing on one-dimensional unsteady state heat conduction problem in isotropic materials which can be solved by separation-of-variables method, the performance of unsteady state heat conduction in anisotropic materials was analyzed. And the unsteady state temperature field of the anisotropic plane wall was obtained. The results will provide help for the energy conservation of anisotropic materials.
2484
Authors: Shun Yu Su, Qin Huang
Abstract: Separation-of-variables method is one of the analytical solution methods to solve unsteady state heat conduction problems. But unsteady state conduction with heat source is an inhomogeneous problem. It can not be solved by separation-of-variables method directly. The combination of variables division method and separation-of-variables method was applied in this paper to deal with heat conduction with heat source in an infinite plate wall. The problem was divided to a steady state and inhomogeneous heat conduction problem, and an unsteady state and homogeneous heat conduction problem by variables division method. The steady state and inhomogeneous problem can be integrated directly. The unsteady state and homogeneous problem can be transformed to the problem that can be solved by separation-of-variables method directly through variable substitution. The unsteady state temperature field in the infinite plate wall was then obtained.
4364
Authors: Shun Yu Su, Jian Chen, Chun Zhi Zhang
Abstract: In this paper, mechanism of anisotropic material of thermal conductivity was revealed by rotating the original rectangular axes so as to determine the principal axes and make the cross-derivative terms disappear. The results indicated that the heat flux vector is commonly not perpendicular to the isothermal surface in anisotropic material. The advantage of anisotropic material of thermal conductivity was analyzed. The application of laminated composite with anisotropic thermal conductivity in double skin envelope was proposed to avoid its disadvantage. The interior envelope in double skin system may be made of laminated glaze or other laminated materials. Basing on the combine of anisotropic material and double skin envelope, the indoor cooling and heating load decrease in summer and winter respectively while the anisotropic material was used as interior building envelope. Especially in summer, the effect of energy saving is obvious since the partial magnitude of conductive heat in the interior envelope could be brought out from the cavity by natural ventilation through it.
829
Authors: Shun Yu Su, Su Yi Huang, Jian Chen
Abstract: Flow boiling heat transfer in vertical narrow annular channels with dual tube heating has been experimentally investigated using distilled water as the working fluid. The experiments were made on two types of test section within the experimental range: heat flux, 40-210 kW/m2; mass flux, 45-180 kg/m2s; system pressure, 2-3.5MPa; gap size, 2mm and 3mm. The intention of this paper is to experimentally survey the flow boiling dryout mechanism of liquid film on the tube wall of vertical narrow annular channels with heated length of 1300mm. The values of dryout temperature, while the heating rate reaches critical heat flux, could be measured in the experiments. And the values of the critical quality xcr were calculated by thermodynamic equilibrium. The main factors which have influence on critical quality, such as mass flux, dimension of the narrow channel, heat flux and water inlet temperature were analyzed based on the experimental data. The empirical correlation which used to calculate critical quality in vertical narrow annular channels in similar conditions was given here. The calculation results of this correlation were compared with experimental data and agreed well with it while the deviation is less than 15%.
209
Authors: Shun Yu Su, Tian Tian, Jian Chen
Abstract: The mechanism of fluid flow and heat transfer in the heat exchangers was investigated in this paper. Using R22 as the working fluid, the steady distributed parameter models of condenser and evaporator in a residential split air-conditioner were established based on thermophysical laws such as mass, momentum and energy conservation equations. The regions of two-phase fluid and superheated gas in evaporator and the regions of superheated gas, two-phase fluid and subcooled liquid in condenser were respectively simulated under designed conditions of air-conditioning system. Based on the calculated results, the flow and heat transfer performances of heat exchangers were analyzed. The results show that the two-phase fluid regions in both evaporator and condenser have great influence on the fluid flow and heat transfer performances in it.
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