Windows controlling heat loss

Dix and Lavan conducted studies to measure the effectiveness of draperies and other indoor shading devices on the coefficient of thermal transmission, U, under winter and summer conditions (89)- With the aid of two environmentally controlled chambers and thermistors located near a test window, they determined that a medium-colored drapery with a white plastic backing reduced conductive heat loss in the winter by 6-1%, and conductive and radiant (solar) heat gains in the slimmer by 33%. Because shades inside casements were more effective than draperies in reducing heat loss under winter conditions, they concluded that the ability of the material to block air flow was more important than other properties of the material used (8 ). 

Ambient temperature changes are one of the reasons for appearance of temperature gradients in the machine and part, and in fact, when the maximum accuracy has to be obtained, the machines are located in temperature-controlled rooms or enclosures. Nevertheless, in more conventional situations, there are some other more important reasons for the temperature gradients heat loss from the motors, radiation from the sun to the machine through the shop windows, heat loss at the main spindle and other moving components (slideways, ball nuts), and the heat produced in the machining process, which is transferred directly to the tool, part, and especially to the chips. 

Window film A coated flexible polymer film that can be used in a window for thermal control, either by reducing solar isolation or by radiant heat loss. 

Heating was provided by two heating tapes one for the preheater and the other for the reactor to compensate for thermal losses from the windows. The gas phase temperature was controlled by manual adjustment of the input voltage to the heating tapes. Thermal Insulation was provided by l"-thick layer of Fiberfrax (The Carborundum Co.). 

The load is a combination of uncontrolled variables which places a particular demand on the control system. Like a manipulated variable, the load is flow or a function thereof. In a mass transfer operation, the load is mass flow. In a level-control loop, for example, where one flow is manipulated, the load is the algebraic sum of all the other flows entering the vessel. The manipulated variable must be matched to the load in order to maintain constant level. In an energy transfer operation, it is the flow of energy. To control temperature of a room, for example, as much heat must be added as is lost.. Heat is lost through doors, windows, etc., and varies with inside and outside temperatures and wind velocity. The sum of these losses (flows) is the load on the heating system. 

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