Ingeniero mecanico

Calculating Heat Loss Calculo de pérdida de calor by Mark Crombie, Chromalox January 30, 2006 ARTICLE TOOLSEmailPrintReprints Share Enlarge this picture |
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Figure 1. This sectional view of a typical pipe system consists of the pipe, insulation, a weather barrier and gaps between each layer.La figura 1. Sección transversal de sistema típico una tubería, el cual consiste en tubería,aislamiento, capa de aire y las diferentes capas. |
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Before plunging headfirst into a myriad of heat trace designs, products and applications, one must first have an understanding of the basics of heat loss.Antes de zambullirse headfirst en una miríada de diseños de traza de calor, productos y aplicaciones, uno debe tener una comprensión de los fundamentos de la pérdida de calor.This articledeals with the basic principles of heat transfer and the calculations used for pipes and vessels. By understanding fundamental heat transfer concepts, you can use them used to arrive at a general formula that is used in heat loss calculations. Figure 1 depicts a sectional view of a typical pipe system. It consists of the pipe, insulation, a weather barrier and gaps between each layer. If the pipeand its contents are warmer than the surrounding environment, heat will be transferred from the pipe to the air. If enough heat is transferred out of the pipe, the pipe contents may thicken or solidify, resulting in damage to pipes or pumping equipment. Heat flows from one object to another in much the same way as water. Objects of unequal temperatures in a thermal system tend toward thermalequilibrium. The hotter object transfers some of its heat to the colder object until the objects are the same temperature. Heat can be transferred by way of conduction, convection and radiation. En este artículo se ocupa de los principios básicos de la transferencia de calor y los cálculos utilizados para tuberías y recipientes. Para comprender los conceptos de transferencia de calor, Ud. puedeutilizarlos para llegar a una fórmula general en los cálculos de la pérdida de calor. La figura 1 muestra una vista Seccional de un sistema de tubería típica. Consiste en la tubería, aislamiento, una barrera de clima y las diferencias entre cada capa. Si la tubería y su contenido es más cálido que el medio ambiente circundante, el tubo transferirá el calor al aire. Si el calor es transferido fuera de latubería, el contenido de la tubería puede espesar o solidificar, resultando en daños a las tuberías o equipos de bombeo. El calor fluye desde un objeto a otro en gran parte del mismo modo que el agua. Los objetos con diferentes temperaturas dentro de un sistema térmico tienden a equilibrarse en su temperatura. El objeto más caliente transfiere su calor al objeto más frío hasta que los objetosigualen su temperatura. El calor puede ser transferido por conducción, convección y radiación.Conduction.Conduction is defined as transferring heat or electricity through a conducting medium by way of direct contact. The rate of heat transfer is dependent upon how much resistance exists between objects of differing temperatures. In many cases, the transfer of heat from one medium to another is desired.Cooking is an everyday example of intended heat transfer. Also, most electronic components operate more efficiently if excess heat generated by the equipment is dissipated to a medium not adversely affected by the addition of heat. In contrast, preserving heat in a system can be just as important as heat transfer. Keeping a pipe’s contents above freezing in cold weather is a common practice ofminimizing heat transfer. Whether a substance acts as a thermal conductor or insulator depends on the thermal resistive properties of the substance. Thermal resistance (R) is a measure of an object’s ability to retard heat transfer by way of conduction through a given thickness of the substance. Mathematically, R is:Conducción Conducción es definido como la transferencia de calor o electricidad a...