Q Amount of heat

Figure 2.10 illustrates how heat pumps can transport heat from a lower to a higher elevation and thereby can cool an already cold temperature substance, such as LH2. The heat pump removes Q, amount of heat from the cold process at the cost of investing W amount of work and delivers Qh quantity of heat to the warm reservoir. In the lower part of Figure 2.10, the idealized temperature entropy cycle is shown for the chiller. The cycle consists of two isothermal and two isentropic (adiabatic) processes ... 

AT = the change in temperature Q = amount of heat required to achieve AT. 

Q = amount of heat transferred in unit time, k = thermal conductivity of the medium, and X = distance between planar siufaces. 

Q = amount of heat transferred from the steam to the liquid per unit time and per unit of heat transfer area A = cross-sectional area of the inner tube V = average velocity of the liquid (assumed to be constant)... 

Generally, q is small because the outside area is not large in comparison to the amount of heat being transferred, and the energy balance can be simplified. In these conditions it is also convenient to write balances over a differential section of the column. These balances yield the following ... 

Here Q is the amount of heat contained per unit volume in the substrate, jc is the distance down into the substrate, and t is the time of inadiation. The solutions of this equation depend on the physical conditions of the uradiation. Thus if the surface is subject to a constant energy supply, Qq, the solution is... 

The thermal condition of the feed is designated as q, and is approximately the amount of heat required to vaporize one mole of feed at the feed tray conditions, divided by the latent heat of vaporization of the feed. One point on the q line is on the 45° line at Xp. 

Thermochemistry is concerned with the study of thermal effects associated with phase changes, formation of chemical compouncls or solutions, and chemical reactions in general. The amount of heat (Q) liberated (or absorbed) is usually measured either in a batch-type bomb calorimeter at fixed volume or in a steady-flow calorimeter at constant pressure. Under these operating conditions, Q= Q, = AU (net change in the internal energy of the system) for the bomb calorimeter, while Q Qp = AH (net change in the enthalpy of the system) for the flow calorimeter. For a pure substance. 

Heat flow (q) The amount of heat flowing into a system (+) or out of it (—),... 

If a body absorbs an amount of heat Q from a reservoir at temperature T, and at the same time does work A,... 

We have assumed that the temperatures remain constant during the transference of a finite amount of heat Q, which implies that the heat reservoirs have very large heat capacities. To remove this restriction, we suppose that the amount of heat absorbed is infinitesimal, SQ. Then, for the gain of available energy we have ... 

Let AU denote the change of intrinsic energy, and let Q be the amount of heat absorbed at the temperature T, in any part of the process. Then, according to the first law ... 

SQ) = (yp h1),- ( Q)p = (r4l%-Thus, cv, cp are the amounts of heat absorbed per unit increase of temperature at constant volume and at constant pressure respectively. They are the specific heats at constant volume and at constant jwessare respectively. 

As a first assumption we take Q independent of temperature, i.e.y we suppose that the same amount of heat is absorbed when a... 

Equation (4.3) is exactly true only if q is an infinitesimal amount of heat, causing an infinitesimal temperature rise, dr. However, unless the heat capacity is increasing rapidly and nonlinearly with temperature, equation (4.3) gives an accurate value for Cp at the average temperature of the measurement Continued addition of heat gives the heat capacity as a function of temperature. The results of such measurements for glucose are shown in Figure 4.1.2... 

Close to the wall, the fluid velocity is low and a negligible amount of heat is carried along the pipe by the flowing fluid in this region and Q is independent of y. 

A parallel reactor system has an extra degree of freedom compared with a series system. The total volume and flow rate can be arbitrarily divided between the parallel elements. For reactors in series, only the volume can be divided since the two reactors must operate at the same flow rate. Despite this extra variable, there are no performance advantages compared with a single reactor that has the same total V and Q, provided the parallel reactors are at the same temperature. When significant amounts of heat must be transferred to or from the reactants, identical small reactors in parallel may be preferred because the desired operating temperature is easier to achieve. 

A 7 depends on q, the amount of heat transferred. As an example, the transfer of 50 J of heat to an object causes an increase in temperature that is twice as large as the increase caused by 25 J of heat. 

AT — In this equation, q is the amount of heat transferred, n is the number of moles of material Involved,... 

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