Thermal resistance definition

Thermal resistance due to fouling has to be included in the calculation of the overall heat transfer coefficient. By definition, the overall heat transfer coefficient is the reciprocal of the overall thermal resistance. Thus, including the thermal resistance due to fouling, it follows... 

Properties The thermal conductivity is given to be ft = 0.78 W/m K. Analysis This problem involves conduction through the glass window and convection at its surfaces, and can best be handled by making use of the thermal resistance concept and dravring the thermal resistance network, as shown in Fig. 3-12. Noting that the area of the window is 71 - 0.8 m X 1.5 m = 1.2 m, the individual resistances are evaluated from their definitions to be... 

There are many applications where radiation is combined with other modes of heat transfer, and the solution of such problems can often be simplified by using a thermal resistance Rq, for radiation. The definition of Rth is similar to that of the thermal resistance for convection and conduction. If the heat transfer by radiation, for the example in Fig. 1.10, is written... 

Shape Factor and Thermal Resistance in Orthogonal Curvilinear Coordinates. The definition of thermal resistance of a system (total temperature drop across the system divided by the total heat flow rate) yields the following general expression for the thermal resistance R and the conduction shape factor S ... 

Resistance Definition. The instantaneous thermal resistance for the three boundary conditions is defined as R = (T(a, t) - TjlQ where Q = q(a, ()4ita2. The results given above yield the following expressions. 

The definition of Adiabatic calorimeters, in spite of being simplified (it does not mention the value of the thermal resistance, always referred to in the past) effectively covers all calorimeters considered by thermochemists as being really adiabatic. This definition was kept for the active adiabatic calorimeters" described in section 4.3. 

Definition Thermoplastic with exc. chem./thermal resist., low coeff. of friction, high elec, insulation, high stress crack resist., chem. inertness, toughness, flexibility, nonaging and nonstick chars., negligible moisture absorp. 

It is useful at this point to consider the definition of an additive as given by the EC (European Commission) an additive is a substance, which is incorporated into plastics to achieve a technical effect in the finished product, and is intended to be an essential part of the finished product. Since the very early stages of the development of the polymer industry, it was realized that useful materials could only be obtained if certain additives were incorporated into the polymer matrix, in a process normally known as compounding. Additives confer on plastics significant extensions of properties in one or more directions, such as general durability, stiffness and strength, impact resistance, thermal resistance, resistance to flexure and wear, acoustic isolation, etc [86]. 

Since thermal resistances are additive, they are very convenient to work with in calculating heat transfer. From the basic definition,... 

People found that some natural stones and some clays had better thermal resistance than others. In particular, some stones or clays exhibited better refractoriness than others. A simple definition of refractoriness is that the material will not melt or deform (shrink) under prolonged service in the furnace environment in service. Excessive shrinkage almost always results in the opening of joints in a furnace, cracking, increased susceptibility to thermal shock, and a host of other problems. 

Aesthetic properties are of greatest concern in decorative laminates. These include gloss, appearance, cleanabiUty, wear resistance, stain resistance, and other surface properties. Physical properties are of most importance for industrial laminates. These include strength, electrical and thermal properties, expansion coefficient, and punchabiUty. The definitions of the laminate grades in these standards foUow. 

In the methods reported above, the temperature change AT used to measure the heat capacity C(T) was supposed to be so small that the time constant r = R C could considered constant in the AT interval. Let us consider, for example, the thermal discharge of a system with heat capacity C(T) a T and thermal conductance to the bath G(T) a T3 (e.g. a metal sample and a contact resistance to the bath at rB). A AT/TB = 10% gives a At/t = 20% over the interval AT, that is a time constant definitely not constant. 

The method of field-induced thermally stimulated current (FITSC) consists of measuring— according to a definite (usually linear) heating scheme—the currents generated by the buildup and release of a polarized state in a high-resistivity solid... 

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