Font Size: a A A

Three - Dimensional Numerical Simulation Study On Flow Characteristics Of Heating Water Tank Of Home Solar Water Heat Water

Posted on:2014-05-30Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhangFull Text:PDF
GTID:2133330422488330Subject:Agricultural Biological Environmental and Energy Engineering
Abstract/Summary:PDF Full Text Request
A heat storage water tank is common in people’s life, it is one of the mostimportant energy storage element. The quantity of useful heat that can be extractedfrom a tank is an important factor to measure the quality of tank design and the waysof water extraction. In the commonly used ways top water-ways, there is a mixingbetween the cold water from the bottom and the hot water in the tank, it will reducedthe quantity of the utilized heat, thus research the level of temperature stratification intank can optimize design of tank and ways of water intake, and raise the efficiencyof energy application.In order to analyse the thermal stratification in the storage tank, it choosed sometanks which are widely used in the south of China to model, use experiment andnumerical simulation to research these tanks. In this paper, the dischargingtemperature profiles of three inlet velocities in laminar were discussed, analyzed themixing and the temperature stratification degree of the tanks in various flowvelocities, set up the mathematical model including the control equations, boundaryconditions and the physical parameters of the water. A comprehensive analysis of thetransient characteristics of the heat storage water tank was also made, to provide asolid theoretical foundation for practical engineering applications.The research content in this paper is summarized as follows:Firstly, the discharging temperature profiles of three inlet velocities in laminarwere studied via experiment, these discharging temperature profiles reflects that theprocess of discharging can be divided into three stages: the invariable hightemperature stage, the stage of outlet temperature reduced fast and the stage of outlettemperature invariable. The time of each stage and the speed have the direct influenceon the temperature. And calculated the exothermal efficiency relative to303K, itshowed that exothermal efficiency decreased with the increase of flow velocity.Secondly, a comparative study is carried out by numerical simulation on thesame dimensions and structures tank. Find the the trends presented in the discharging temperature profiles obtained and the exothermal efficiency by experiments andnumerical simulation are basically the same, indicating that the developed numericalmodels can be used to simulate tanks.Thirdly, using the validated method simulate the horizontal and vertical tanks onthe3D temperature contour, the discharging temperature profiles and the level oftemperature stratification under different working conditions, and used adimensionless exergy parameter quantify the level of temperature stratification. Theresults show that with the increase of inlet velocity, the mixing increasing, and thelevel of temperature stratification decreasing, and placing the inlet and outlet on thesame side is better than placing them at the opposite sides, a vertical tank is betterthan a horizontal one. Hence, small inlet velocity, a vertical tank placing the inlet andoutlet on the same side has a better level of temperature stratification.Finally, a optimal design scheme was proposed according to the simulationresults, The results show that this scheme had certain to improve the level oftemperature stratification for the200L small household tank, but the effect was notsignificant. TRNSYS was also used for simulating discharging, and compared withthe results of FLUENT.
Keywords/Search Tags:Heat Storage Water Tank, Three-dimensional Numerical Simulation, Discharging Temperature Profiles, Thermal Stratification, Dimensionless Exergy
PDF Full Text Request
Related items