Specific heat defined

If excess specific heat, defined as that part of the specific heat that is due to the structural phase transition (cf Salje, 1988), is denoted by ACpexcess,trans> the excess entropy associated with transition within the upper and lower limits of Cp perturbation is given by... 

The heat required to raise the temperature of a substance is called the specific heat, defined as the amount of heat energy required to raise the temperature of 1 g of substance by 1°C. It can be expressed by file equation... 

It is not practical to determine the contact resistance in power connectors. The resistance of the connection of a specified length of conductor on each side of the connector is measured and is called the overall resistance or the connection resistance. One industry specification (32) defines the included lengths and requites the stabiUty of the connection resistance to be within 5% of its average value throughout the heat-cycle test. 

Parameters Cj and Cj are specific heats of the cold and hot fluids in Btu respectively, and the log-mean temperature difference is defined as follows ... 

In order to identify the production processes required to produce a particular product you need a production requirement in the form of product specifications which define the features and characteristics of the product that are to be achieved. By studying these specifications you will be able to identify the processes required to turn raw materials and bought-out components into a finished product. With manufactured products the processes may include machining, welding, fabrication, assembly, forming, plating, painting, heat treatment, etc. 

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. ... 

The specific heat of a substance must always be defined relatively to a particular set of conditions under which heat is imparted, and it is here that the fluid analogy is very liable to lead to error. The number of heat units required to produce unit rise of temperature in a body depends in fact on the manner in which the heat is communicated. In particular, it is different according as the volume or the pressure is kept constant during the rise of temperature, and we have to distinguish between specific heats (and also heat capacities) at constant volume and those at constant pressure, as well as other kinds to be considered later. 

Prior to the now almost universal adoption of the SI system of units, the unit of heat was defined as the quantity of heat required to raise the temperature of unit mass of water by one degree. This heat quantity is designated the calorie in the cgs system and the kilocalorie in the mks system, and in both cases temperature is expressed in degrees Celsius (Centigrade). As the specific heat capacity is a function of temperature, it has been necessary to set a datum temperature which is chosen as 298 K or 25°C. 

In Fig. 2.36 the dimensionless heat flux q is plotted versus the difference (Ti ax — Ts). The dimensionless heat flux is defined as q = [ /(GCpA7 )](7iiax/7iiean), where q is the heat flux, G is the mass flux, Cp is the specific heat, AT Ts — Tja, Ts is the saturation temperature, Tin is the water temperature supplied to the inlet collector, and Tmax and Tmean are maximum and average temperature of the heated surface, respectively. The term qj(GcpAT) reflects the effect of subcooling. 

Here u, T, and C are fluid velocity (a vector), temperature, and concentration of reactive species these are the principal variables in our formulation. Other parameters are density (p), pressure (p), viscosity (q), specific heat (c), thermal conductivity (k), and species diffusivity (D). The V operator is defined as V -(a/ax,a/ay). 

We thus label heat capacity as Cp, meaning the thermal capacity at constant pressure. Sometimes, it is also called specific heat, meaning the ratio of thermal capacity of any given material to that of water, defined as 1.000. 

Table 1.6 Characteristic quantities to be considered for micro-reactor dimensioning and layout. Steps 1, 2, and 3 correspond to the dimensioning of the channel diameter, channel length and channel walls, respectively. Symbols appearing in these expressions not previously defined are the effective axial diffusion coefficient D, the density thermal conductivity specific heat Cp and total cross-sectional area S, of the wall material, the total process gas mass flow m, and the reactant concentration Cg [114].

Define the following terms a. temperature b. heat and c. specific heat capacity. 

Here 0 is the Heaviside function. The projection operator formalism must be carried out in matrix from and in this connection it is useful to define the orthogonal set of variables, k,uk,5k > where the entropy density is sk = ek — CvTrik with Cv the specific heat. In terms of these variables the linearized hydrodynamic equations take the form... 

Even when complete miscibility is possible in the solid state, ordered structures will be favored at suitable compositions if the atoms have different sizes. For example copper atoms are smaller than gold atoms (radii 127.8 and 144.2 pm) copper and gold form mixed crystals of any composition, but ordered alloys are formed with the compositions AuCu and AuCu3 (Fig. 15.1). The degree of order is temperature dependent with increasing temperatures the order decreases continuously. Therefore, there is no phase transition with a well-defined transition temperature. This can be seen in the temperature dependence of the specific heat (Fig. 15.2). Because of the form of the curve, this kind of order-disorder transformation is also called a A type transformation it is observed in many solid-state transformations. 

The limitation of the storage capacity is, as mentioned before, caused by the limitation of entropy change AS within the storage (see Figure 4). For sensible and latent heat storage (so-called direct thermal energy storage) this is defined by the specific heat... 

The transition between crystalline and amorphous polymers is characterized by the so-called glass transition temperature, Tg. This important quantity is defined as the temperature above which the polymer chains have acquired sufficient thermal energy for rotational or torsional oscillations to occur about the majority of bonds in the chain. Below 7"g, the polymer chain has a more or less fixed conformation. On heating through the temperature Tg, there is an abrupt change of the coefficient of thermal expansion (or), compressibility, specific heat, diffusion coefficient, solubility of gases, refractive index, and many other properties including the chemical reactivity. 

A deliquescent material takes up moisture freely in an atmosphere with a relative humidity above a specific, well-defined critical point. That point for a given substance is defined as the critical relative humidity (RH0). Relative humidity (RH) is defined as the ratio of water vapor pressure in the atmosphere divided by water vapor pressure over pure water times 100% [RH = (PJP0) X 100%]. Once moisture is taken up by the material, a concentrated aqueous solution of the deliquescent solute is formed. The mathematical models used to describe the rate of moisture uptake involve both heat and mass transport. 

The choice of a primary thermometer such as the 3He melting pressure thermometer to define the PLTS 2000 witnesses the great difficulties encountered in the measurement of very low temperatures. For example, at the beginning of 1980s, it was realized that differences up to 40% existed in the data of 3He specific heat obtained... 

Ratio of specific heats, variable defined in Chapters 7 and 9... 

Defining the mass weighted specific heat of the mixture as... 

For the plug flow reactor or any similar adiabatic system, it is also possible to define an average specific heat that takes its explicit definition from... 

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