“heat transfer”Search All-EnPress Publisher LLC.

Oct 8, 2021

Study on heat transfer characteristics of regenerative shell-and-tube heat exchangers

A new type of regenerative shell-and-tube heat exchanger is designed to solve the problems that the generation load of cogeneration units is limited by the amount of heat supply during the heating period, the peak shaving capacity of units decreases, and the phenomenon of wind and light abandonment in the power system is serious. Considering the advantages of nearly constant temperature and large potential heat release during the heat storage/release process of

phase change materials, paraffin is selected as the phase change material, and the phase change area of the heat exchanger is selected as the heat exchange unit. The control variates method is used to simulate the heat storage/release process of the heat exchange unit according to the key factors such as the flow rate of heat transfer fluid, the thermal conductivity of phase change materials and the thickness of phase change layer. The results show that increasing the flow rate of heat transfer fluid can enhance the heat storage capacity of the heat exchange unit and shorten the complete melting time of phase change materials. In order to control the heat at the output end of the heat exchanger during the heat release process, the flow rate of heat transfer fluid should be appropriately selected; using composite materials to improve the thermal conductivity of phase change materials can enhance the heat transfer capacity of the heat exchange unit, and the average heat transfer coefficient of the heat exchange unit is more than 2 times higher than that of pure paraffin at the same heat transfer fluid flow rate; increasing the thickness of phase change layer can prolong the time of maintaining the outlet temperature of heat transfer fluid in the process of heat release.

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Dec 14, 2021

Analysis of the influence of the number of venetian blinds on compact heat exchangers

The paper presents a numerical study of compact tube-fin heat exchangers with Venetian blades. The influence of the number of Venetian blades on the thermo-hydraulic characteristics of the exchanger is determined. A 3D numerical model was used in the laminar regime and for a Reynolds number variation, based on the hydraulic diameter between 120 and 1,200. By varying the number of Venetian blinds upstream and downstream of the central Venetian blind, it is

determined that, for smaller numbers of Reynolds fins with 2 Venetian blades, the highest heat transfer coefficient is obtained. On the other hand, by increasing the air velocity at the model inlet, better heat transfer results are obtained for geometries with a higher number of Venetian blades.

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Dec 16, 2019

Exact analysis of MHD Walters’-B fluid flow with non-singular fractional derivatives of Caputo-Fabrizio in the presence of radiation and chemical reaction

The present article reports the applications of Caputo-Fabrizio time-fractional derivatives. This article generalizes the idea of unsteady MHD free convective flow in a Walters.-B fluid with heat and mass transfer study over an exponential isothermal vertical plate embedded in a porous medium. The governing equations are converted into dimensionless form and extended to fractional model. The generalized Walters-B fluid model has been solved analytically using the Laplace transform technique. From the general solutions we reduce limiting solutions when to the similar motion for Newtonian fluid. The corresponding expressions for and Nusselt and Sherwood numbers are also assessed. Numerical results for velocity, temperature and concentration are demonstrated graphically for various factors of interest and discussed. As a result, we have plotted the influence of fractional parameter on fluid flow and drawn comparison between fractional Walters’-B and fractional Newtonian fluid and found that fractional Newtonian fluid is faster than fractional Walters’-B fluids.

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Jul 20, 2022

Energy saving analysis of photovoltaic roof based on MATLAB

One-dimensional unsteady theoretical models of three different photovoltaic module installation modes are established. Through MATLAB modeling and simulation, the influence of photovoltaic modules on roof heat transfer in different layout modes is compared. Comparing with ordinary roof, the shading effect of photovoltaic roof in summer and heat preservation effect in winter was analyzed. The results show that the PV roof layout with ventilation channel is better in summer. The proof layout with closed flow channel is better in winter.

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Apr 9, 2022

Sustainability study of medium-deep geothermal buried pipe for heat supply

In order to study the temperature change trend of the surrounding geotechnical soil during the operation and thermal recovery of the medium-deep geothermal buried pipe and the influence of the geotechnical soil on the operational stability of the vertical buried pipe after thermal recovery. Based on the data of geological stratum in Guanzhong area and the actual engineering application of medium-deep geothermal buried pipe heating system in Xi’an New Area, the influence law of medium-deep geothermal buried pipe heat exchanger on surrounding geotechnical soil is simulated and analyzed by FLUENT software. The results show that: after four months of heating operation, in the upper layer of the geotechnical soil, the reverse heat exchange zone appears due to the higher fluid temperature; in the lower layer of the geotechnical soil, the temperature decreases more with the increase of depth and shows a linear increase in the depth direction; without considering the groundwater seepage, after eight months of thermal recovery of the geotechnical soil after heating, the maximum temperature difference after recovery is 3.02 ℃, and the average temperature difference after recovery is 1.30 ℃ The maximum temperature difference after recovery was 3.02 ℃ and the average temperature difference after recovery was 1.30 ℃. The geotechnical thermal recovery temperature difference has no significant effect on the long-term operation of the buried pipe, and it can be operated continuously and stably for a long time. Practice shows that due to the influence of various factors such as stratigraphic structure, stratigraphic pressure, radioactive decay and stratigraphic thermal conductivity, the actual stratigraphic temperature below 2000m recovers rapidly without significant temperature decay, fully reflecting the characteristics of the Earth’s constant temperature body.

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Oct 19, 2021

Analysis of influence of ripple parameters of heat storage elements on flow and heat transfer performance

In order to study the influence of the corrugated angle and width of enamel heat storage element on the flow and heat transfer performance, a certain enamel heat storage element was numerically simulated by FLUENT software, and the variation curves of internal flow field velocity, temperature distribution, Nusselt number and drag coefficient with Reynolds number were obtained when the corrugated angle and width of the heat storage element were different. The

simulation results show that when the ripple inclination increases from 20° to 60°, the resistance coefficient of the heat storage element increases, and the Nusselt number increases, and the increase of the resistance coefficient is greater than that of the Nusselt number; when the ripple width increases from 6 mm to 10 mm, the increase of resistance coefficient is small, and the increase of Nusselt number is large.

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