The paper presents the results on numerical simulation of the temperature field of a cold plate type liquid heat exchanger for a multichannel transmitter/receiver module. Each side of the cold plate carries 8 local microwave fuel elements with a heat dissipation capacity of 11 W each and one block with low-power electronic elements (total power of all elements — 50 W), installed symmetrically on both sides. The total heat dissipation capacity is 276 W. The cold plate is cooled by pumping a liquid heat carrier (Antifreeze A 65) through a curved cooling channel of rectangular cross-section made inside the liquid heat exchanger. The study was conducted at a working fluid flow rate of 2, 4, 6, 8 and 10 l/min. Numerical simulation allowed obtaining the temperature distribution of the mounting surfaces of the cold plate and determining the values of the working fluid flow rate, which provide effective cooling of the mounting surfaces. It is shown that at a flow rate of 4 l/min, the temperature values at the installation sites of local microwave elements do not exceed 64°C. The total thermal resistance of the cooling system based on a liquid heat exchanger is from 0.063 to 0.028°C/W with a flow rate from 2 to 10 l/min, respectively.
Based on the results of the study of the parameters of the air flow inside of the brass screw-shape tube of the heat exchanger, the determination of their optimal geometric characteristics and further modeling of the stress-strain state was performed. Verification of simulation results is carried out on the basis of comparison with the test task.
The article deals with the research of thermal energy storage tanks. It is proposed to use a «thermal core» to minimize the effects of thermal stratification and high thermal inertia. The thermal core consists of a binary tube placed along the central axis of the tank, filled with a paraffin mixture with a melting point of 45 to 65oC and a density of 0,880 to 0,915g/cm3 at 15oC. In the study the Fluent software package was used to model the temperature distribution in the tank under free convection conditions, the data was then converted to the Transient Thermal module of the ANSYS software package for further calculations of the unsteady temperature distribution in the thermal core. The study showed that a 1400-liter thermal energy storage device, heated for 1 hour by a heat-transfer fluid at 115oC, cools down to 50oC in 4 hours. The research also revealed the need to improve the tank design based on the analysis of the hydrodynamic structure of the flow in the tank, as evidenced by the trajectory distribution of free convective flows. The authors concluded that the use of a heat core, regardless of the type of paraffin used to form it, helps to reduce temperature stratification by height in the tank and that the type of paraffin used has no significant effect on the overall cooling of the tank. However, using ceresin as a core filler results in a slightly higher average tank temperature. Based on the results of the study, the time of complete cooling of the tank was determined by the non-uniform temperature field of all elements of the tank.
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