The present computational fluid dynamics (CFD) study was performed to investigate the 3D turbulent flow and heat transfer of coiled tube-in-tube heat exchangers (CTITHEs). The realizable k-ε model with enhanced wall treatment was used to simulate the turbulent flow and heat transfer in the heat exchangers. Temperature dependent thermophysical properties of water were used and heat exchangers are analyzed considering conjugate heat transfer from hot fluid in the inner-coiled tube to cold fluid in the annulus region. Garbh sanskar by balaji tambe pdf free. After simulations, Taguchi method was used for finding the optimum condition for some design parameters in the range of coil diameter from 0.18 to 0.3 m, tube and annulus flow rates from 2 to 4 and 10 to 20 LPM, respectively. Results show that the Gnielinski correlation used extensively for predicting Nusselt number for turbulent flow in ducts can be used to predict Nusselt number for both inner-coiled tube and annular coiled tube using the friction factor correlation for helical tubes of Mishra and Gupta. Contribution ratio obtained by Taguchi method shows that annulus side flow rate, tube side flow rate, coil diameter, and flow configuration are the most important design parameters in coiled tube-in-tube heat exchangers, respectively. Positive flow response characteristic in vertical tube furnace of supercritical once-through boiler provides a feasible and effective way to alleviate the thermal maldistribution to some extent.

In the present paper, theoretical derivation and simulations were performed to investigate the mechanism and forming conditions of positive flow response characteristic systematically. Two types of transition criterions were built up to judge positive or negative flow response characteristic. Parametric study was carried out to analyze the influencing factors.

Both the operating conditions (mass flux, pressure, temperature or quality, heat flux) and the geometric parameters (inside diameter, length, pitch and type of tube) were investigated. In addition, thermal-hydraulic simulation of a 600 MW supercritical W-flame boiler has been carried out to take all these factors into account simultaneously. The conclusions drawn from this study will be of help to the design of large capacity supercritical once-through boilers as well as the refurbishment of existing supercritical or subcritical boilers.

Mar 1, 2018 - heat flow include single-phase water flow, single-phase steam flow and two-phase flow. Keywords: heat transfer, geothermal wellbore, Initial Formation Temperature. By converting the radiation and natural convection into equivalent thermal. Decision support system, version 1.3, user's manual.

A novel two-phase thermosyphon based on automotive technology is presented as a valid solution for the cooling of power-electronic semiconductor modules. A horizontal evaporator configuration is investigated.

This solution is based on a 90 deg-shaped thermosyphon that allows an optimal geometrical arrangement of the cooler with limited volume occupancy, reduced air pressure drop, and weight as well as optimal thermal performance compared with standard heat-sink technology. The 90 deg-shape refers to the mutual arrangement of the evaporator body and the condenser, which are in a horizontal and vertical position, respectively. The evaporator cools three power modules with a total power loss between 500 and 1500 W. Experimental results are presented for inlet air temperatures ranging from 20 to 50 °C and for different air volume flow rates between 200 and 400 m 3/h. The working fluid is refrigerant R245fa.

The maximum thermal resistance (cooler base to air) attained values between 40 and 50 K/kW. Portable energy storage will be a key challenge if electric vehicles (EVs) become a large part of our future transportation system. A big barrier to market uptake for EVs is driving range. Range can be further limited if heating and air conditioning systems are powered by the EV's batteries. The use of electricity for HVAC can be minimized if a thermal storage system, a “thermal battery,” can be substituted as the energy source to provide sufficient cabin heating and cooling. The aim of this project was to model, design, and fabricate a low-cost, modular thermal battery for EVs.

The constructed thermal battery employs a phase change material erythritol (a sugar alcohol commonly used as artificial sweetener) as the storage medium sealed in an insulated, stainless steel container. At a total prototype cost of ∼$311/kW-h, the system is roughly half the price of lithium ion batteries.