Specific heal capacity

Data from inter alia Sundbcrg 1991), Banks Robins (2002). Halliday Resnick (1978). Italics show recommended values cited by Eskilson el at. (2000). Note that thermal conductivity increases with quartz content, and that most rock materials have a specific heal capacity of around 800 J/kg/K, or slightly over 2 MJ/m /K (compare with copper at only 386 J/kg/K). 

Calculation of specific heal capacity with the needed corrections for heat losses (and gains)... 

The heat capacity of a subshince is defined as the quantity of heat required to raise tlie temperature of tliat substance by 1° the specific heat capacity is the heat capacity on a unit mass basis. The term specific heat is frequently used in place of specific heat capacity. This is not strictly correct because traditionally, specific heal luis been defined as tlie ratio of the heat capacity of a substance to the heat capacity of water. However, since the specific heat of water is approxinuitely 1 cal/g-°C or 1 Btiiyib-°F, the term specific heal luis come to imply heat capacity per unit mass. For gases, tlie addition of heat to cause tlie 1° tempcniture rise m iy be accomplished either at constant pressure or at constant volume. Since the mnounts of heat necessary are different for tlie two cases, subscripts are used to identify which heat capacity is being used - Cp for constant pressure or Cv for constant volume. Tliis distinction does not have to be made for liquids and solids since tliere is little difference between tlie two. Values of heat capacity arc available in the literature. ... 

An open cylindrical tank 500 mm diameter and I m deep is three quarters filled with a liquid ol density 980 kg/mJ and of specific heat capacity 3 kj/kg K. If the heat transfer coefficient from the cylindrical walls and the base of the tank is 10 W/m2 K and front the surface is 20 W/m3 K, what area of heating coil, fed with steam at 383 K. is required to heat the contents from 288 K to 368 K in a half hour The overall heat transfer coefficient for the coil may be taken as 100 W/m2 K, the surroundings we at 288 K and the heal capacity of the tank itself may be neglected. 

ATOMIC HEAT. The product of the gram-atomic weight of an element and its specific heat The result is the atomic heat capacity per gram-atom. For many solid elements, the atomic heal capacity is very nearly the same, especially at higher temperatures and is approximately equal to 3R, where R is the gas constant (Law of Dulong and Petit). 

HEAT CAPACITY. The amount of heal necessary, to raise the temperature of a sysiem, entity, or substance by one degree of temperature. It is most frequently expressed in calories per degree cenrigrade or Btu per degree Fahrenheit, if the mass of a substance is specified, then certain derived values of the heal capacity can be obtained, such as the atomic heat, molar heut. or specific heat. 

The amount of heat required to raise the temperature of unit quantity (1 mole or 1 gram) of a substance by P C without change in phase is called the heal capacity (sometimes called specific heat) of the substance. Values of the heat capacity of substances are given in tables hich may be found in reference books. 

Let US choose as the reference state for each component the system phase (liquid or gas), temperature (Ti), and pressure (I atm). The specific enthalpy of, say, component A in the product stream would be Hs = Cpa(7 3 - T]). (Remember that there are no phase changes and we are assuming constant heal capacities.) The energy balance for this open adiabatic system is AH = 0. or... 

Once an absorbent has been selected, the design of the absorber will require the procurement of tunic physical property data on the absoibenl-absotbale system. In addition to the standard physical properties such as density, viscosity, surface tension, and heal capacity, specific data will be required on vapor-liquid equilibrium and the hent of solution or reaction. 

The MD is a computer simulation technique that allows one to predict the time evolution of a system of interacting particles (e.g., atoms, molecules, granules, etc.) and estimate the relevant physical properties [23,24]. Specifically, it generates such information as atomic positions, velocities, and forces from which the macroscopic properties (e.g., pressure, energy, and heal capacities) can be derived by means of statistical mechanics. 

The spec heat (s) of a substance is the amount of heat required to raise the temperature of 1 g of the substance by 1 C. The heat capacity (C) is the amount of heat required to raise the temperature of an object by 1 C. We can use the specific heat of a substance to determine the heat capacity of a specified quantity of that substance. For example, we can use the specific heal of water, 4.184 J/(g °C), to determine the heat capacity of a kilogram of water ... 

DU EON C AND PETIT LAW OF SPECIFIC HEATS. Ii has long been known Ural the atomic heals of Ihe great majority of elements have nearly the same value at room temperature in fact, the thermal capacity of a gram-atom of most elements is not far from 6 calories per degree. Dulong and Pelit expressed this by stating that the specific heats of elements arc in inverse proportion to their atomic weights. 

Q, now measures the heal absorbed under constant pressure, and c, is the constant pressure specific heat. Since the right side of Equation (2) contains three quantities, a mere choice of a mass unit and a degree unit is insufficient to establish a unit of heal. It is necessary to select some substance as a standard reference body and assign an arbitrary value of, say cp equal to unity for it. Water is the universal choice for this standard body due not only to its cheapness and ease nf purification, hut also to its large heat capacity. 

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