On the Thermal Performance of the Vapor Chamber with Micro-channel for Unmixed Air Flow Cooling

Numerical and experimental results on the thermal performance of vapor chamber with and without micro-channel under constant heat flux are presented. The mathematical model of the vapor chamber is a two-phase closed chamber with wick sheet and a wick column. A finite volume method with structured uniform grid method system is applied to solve the model. Effects of micro-channel on the temperature distribution of the vapor chamber are considered. The results obtained from the model are verified with those from the measured data. The experimental tests are carried out and good agreement is obtained with the numerical results. These numerical results are useful for the design to improvement thermal performance of the vapor chamber and also diminished the expense and time of the real test

Thermal Performance Analysis of a Newly Designed Circular Firewood Boiling Salt Stove

Different biomass stoves are introduced and distributed among people living in rural and urban areas, especially in developing countries. For salt crystal production in Thailand’s rural north-eastern area, open fire stoves are used in domestic and small productive activities. Their thermal efficiency is very low for converting heat into utilization energy. A new stove with a circular configuration was designed and constructed to consider its thermal efficiency and economics, which were compared with those from a traditional and an improved traditional stove. The obtained thermal efficiency of the newly designed stove was 14.77% higher than that of the improved stove and 81.45% higher than that of the traditional stove. For the same initial saline volume, the final amounts of salt crystals and salt flowers obtained from the newly designed stove was higher compared with those obtained from the improved stove and the traditional stove, respectively, resulting in a 69.25% shorter payback period

Numerical study on air ventilation in the workshop room with multiple heat sources

In the present study, the application of computational fluid dynamic (CFD) to analyze air quality and thermal distribution in the workshop room with the multiple heat sources are investigated. In numerical study, a three-dimensional of a single-phase turbulent flow model is employed to analyze temperature distribution and fluid flow in workshop room. The initial and boundary conditions of the models are based on the experimental data. By solving the equations of continuity, momentum, and energy, the velocity and temperature distributions of air within workshop room are presented. It was found that the predicted air temperature and air velocity within the workshop room are consistent with the experimental results. The ventilation system positions and the installed position of equipment inside the workshop have significant effect on suction force which results in the accumulated heat and transport air pollution within the workshop room. The obtained results of the study are expected to lead to guidelines that will allow the designing the ventilation of air-cooling system to transport air pollution and accumulated heat for large workshop room coupled with multiple heat sources. Keywords: Ventilation system, Workshop room, Temperature distributio

A review of flow and heat transfer characteristics in curved tubes

The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. In general, these techniques can be divided into two groups: active and passive techniques. The active techniques require external forces, e.g. electric field, acoustic or surface vibration, etc. The passive techniques require fluid additives or special surface geometries. Curved tubes have been used as one of the passive heat transfer enhancement techniques and are the most widely used tubes in several heat transfer applications. This article provides a literature review on heat transfer and flow characteristics of single-phase and two-phase flow in curved tubes. Three main categories of curved tubes; helically coiled tubes, spirally coiled tubes, and other coiled tubes, are described. A review of published relevant correlations of single-phase heat transfer coefficients and single-phase, two-phase friction factors are presented.Curved tube Heat transfer characteristics Flow characteristics Helically coiled tube Spirally coiled tube Pressure drop Heat transfer coefficient Friction factor