In this study, in order to increase the heat transfer rate in concentric double-pipe heat exchangers by an active method, a rotating ball valve was mounted downstream of the outer pipe end and used as a pulse generator. In the experimental set-up, hot water (40-70 °C) was passed through the inner pipe with fixed mass flow rate (Reynolds number ≈ 10,200) while cold water was passed through the a...

This experimental study is intended to explore the heat performance of a novel vacuum tube heat collector with thermal storage. In order to enhance the heat transfer performance, we add radial metal fins to the U-tube which is used as the heat transfer channel of water. Meanwhile, in order to increase the thermal capacity of the heat collector, the heat collector model is designed to be larger ...

Aluminum alloy castings are normally water quenched after solution treatment to improve mechanical properties. Rapid water quenching can result in high-residual stress and severe distortion which significantly affect functionality and performance of the products. To optimize product design and durability, one needs to model and predict residual stress and distortion produced in the water-quench...

double-diffusive mixed convection in a lid-driven square enclosure filled with al2o3-water is numerically investigated. two-dimensional nonlinear governing equations are discretized using the control volume method and hybrid scheme. the equations are solved using simpler algorithm. the results are displayed in the form of streamlines, isotherms, and iso-concentrations when the richardson number...

A method to obtain the local heat transfer coefficients of carbon dioxide at supercritical pressures in vertical multi-port mini-channels and in a vertical small tube under cooling conditions was presented through the combination of experiments and numerical simulation in this paper. The CFD code FLUENT 6.1 was used to simulate the convection heat transfer of cooling water to determine the loca...

Nowadays, microchannels as closed circuits channels for fluid flow and heat removal are an integral part of the silicon-based electronic microsystems. Most of previous numerical studies on microchannel heat sinks (MCHS) have been performed for a two-dimensional domain using constant properties of the working fluid. In this study, laminar fluid flow and heat transfer of variable properties Al2O3...

We investigate using transient non-equilibrum molecular dynamics simulation the temperature relaxation process of three structurally different proteins in water, namely; myoglobin, green fluorescence protein (GFP) and two conformations of the Ca(2+)-ATPase protein. By modeling the temperature relaxation process using the solution of the heat diffusion equation we compute the thermal conductivit...

1. The ability of fish gills to transfer heat was measured by applying a heat pulse to blood in the ventral aorta and measuring it before and after passing through the gills of a teleost, Hemitripterus americanus. 2. 80-90% of heat contained in the blood is lost during passage through the gills. 3. The fraction of heat not lost during passage through the gills is due to direct transfer of heat ...

An experimental study is reported on natural convection heat transfer from a helical heating coil to the surrounding fluid. The coil is heated electrically and the surrounding fluid is selected to be water. The range of parameters are: Rayleigh number, 879 ?£ Ra ?£ 780168, Prandtl number, 4.22 ?£ Pr ?£ 10.02, dimensionless coil diameter,7.69 ?£ Dave /d ?£ 10.77, number of coil rings, 2 ?£ N ?£ ...

The conventional liquids have some limitations regarding the thermal properties. The nanoparticles addition is one of the techniques which can modify them. In this research, heat transfer coefficient (h) and pressure loss (Δp) of various nanofluids containing Al2O3, SiO2 and MgO nanoparticles dispersed in water in an annular tube with constant wall temperature were numerically considered. Accor...