Experimental data of heat transfer coefficient during evaporation of R-1234yf, R-134a, and R-22 in horizontal circular small tubes are compared. The local heat transfer coefficient is obtained for heat fluxes ranging from 10 to 35 kW [m.sup.-2], mass fluxes ranging from 100 to 650 kg [m.sup.-2] [s.sup.-1], saturation temperatures of 5,10, and 15[degrees]C, and quality up to 1.0. The test sectio…

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This article presents a mathematical model for heat exchanger network synthesis with environmental and economic impacts considered simultaneously, and an example of its application is presented. The mathematical model deals with environmental impact as a factor of objective function. At first, economic and environmental factors are normalized by their maximum values over the parameter space (D…

Combined power generation or cogeneration is a highly effective technology that produces heat and electricity in one device more efficiently than separate production. Overall effectiveness is growing by use of combined technologies of energy extraction, taking heat from flue gases and coolants of machines. Another problem is the dependence of such devices on fossil fuels as fuel. For the com…

In the present paper parallel particle swarm optimization algorithm is used for optimization of a cross flow plate fin heat exchanger with consideration of entropy generation. A total number of seven geometrical design parameters, namely, hot fluid length, cold fluid length, length of the fin, height of the fin, frequency of the fin, thickness of the fin, and number of layers of hot side, are c…

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In this article, an approximate analytical solution of flow and heat transfer for a viscoelastic fluid in an axisymmetric channel with porous wall is presented. The solution is obtained through the use of a powerful method known as Optimal Homotopy Asymptotic Method (OHAM). We obtained the approximate analytical solution for dimensionless velocity and temperature for various parameters. The …

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To assist student understanding of heat transfer through woody stems, we developed an instructional package that included an Excel-based, one-dimensional simulation model and a companion instructional worksheet. Guiding undergraduate botany students to applying principles of thermodynamics to plants in nature is fraught with two main obstacles: (1) students have a limited knowledge of heat t…