Heat capacity transfer rate

Reactor heat carrier. Also as pointed out in Sec. 2.6, if adiabatic operation is not possible and it is not possible to control temperature by direct heat transfer, then an inert material can be introduced to the reactor to increase its heat capacity flow rate (i.e., product of mass flow rate and specific heat capacity) and to reduce... 

Stream Supply temp. T, rc) Target temp. Tr rC) AH (MW) Heat capacity flow rate CP (WN C- ) Heat transfer coefficient h(MW... 

These are also known as the Number of Transfer Units or NTIJ for short. We suggest TVi be characterised as the dimensionless transfer capability of the heat exchanger. Instead of N2 the ratio of the two heat capacity flow rates... 

Here P indicates the effectiveness of the heat exchanger (to be elaborated in Section 7.4) and R (from its definition) is the ratio of the heat-capacity flow rates Note the change in nomenclature from subscripts h and c to t and s, the latter two referring to tube and shell, respectively. An important fact is that whether the hot (or cold) fluid is flowing in the shell side or in the tubes has no effect on F as long as the heat transfer to the ambient is negligible. Otherwise, the cold fluid should be in the shell side to reduce heat losses Combination of Eqs (7.28) and (7.29) gives... 

In Figure 14.26, the instantaneous efficiency and the outlet temperature of a liquid-type collector (single-covering, steel finned tubes, black absorber) are illustrated as a function of liquid heat capacity flow rate [37]. The parameter is the irradiation. As the variations of I are accompanied by nonlinear heat transfer resistance variations, the curves for different I values deviate. The entry temperature of the medium is equal to the outside temperature (T j = TJ. 

Consider the schematic of a countercurrent heat exchanger in Figure 10.11. The hot stream, having a heat-capacity flow rate of C, enters at 7), and exits at It transfers heat... 

The cold stream has a heat-capacity flow rate C = 40,000 Btu/hr-°F. Its heat transfer coefficients are A, = h - 50 Btu/(ft -hr-°F). For a stainless steel heat exchanger with a floating head, built to withstand pressures up to 100 barg, estimate the bare-module cost. 

Solution Polymerization. In this process an inert solvent is added to the reaction mass. The solvent adds its heat capacity and reduces the viscosity, faciUtating convective heat transfer. The solvent can also be refluxed to remove heat. On the other hand, the solvent wastes reactor space and reduces both rate and molecular weight as compared to bulk polymerisation. Additional technology is needed to separate the polymer product and to recover and store the solvent. Both batch and continuous processes are used. 

Continuous polymerization systems offer the possibiUty of several advantages including better heat transfer and cooling capacity, reduction in downtime, more uniform products, and less raw material handling (59,60). In some continuous emulsion homopolymerization processes, materials are added continuously to a first ketde and partially polymerized, then passed into a second reactor where, with additional initiator, the reaction is concluded. Continuous emulsion copolymerizations of vinyl acetate with ethylene have been described (61—64). Recirculating loop reactors which have high heat-transfer rates have found use for the manufacture of latexes for paint appHcations (59). 

Amplitude of controlled variable Output amplitude limits Cross sectional area of valve Cross sectional area of tank Controller output bias Bottoms flow rate Limit on control Controlled variable Concentration of A Discharge coefficient Inlet concentration Limit on control move Specific heat of liquid Integration constant Heat capacity of reactants Valve flow coefficient Distillate flow rate Limit on output Decoupler transfer function Error... 

Air-cooled condensers are used mostly in air-conditioning and for smaller-refrigeration capacities. The main advantage is avauability of cooling medium (air) but heat-transfer rates for the air side are far below values when water is used as a coohng medium. Condensation always occurs inside tubes, while the air side uses extended surface (fiusy... 

With the introduction of mechanical refrigeration, the term ton was retained. The owner could now buy a system capable of providing the equivalent capacity of hov/ever many tons was needed. Since one pound of ice absorbs 144 Btu when melting, one ton of ice melting over a period of 24 hours has a heat transfer rate equivalent to the following ... 

In the case of a temperature probe, the capacity is a heat capacity C == me, where m is the mass and c the material heat capacity, and the resistance is a thermal resistance R = l/(hA), where h is the heat transfer coefficient and A is the sensor surface area. Thus the time constant of a temperature probe is T = mc/ hA). Note that the time constant depends not only on the probe, but also on the environment in which the probe is located. According to the same principle, the time constant, for example, of the flow cell of a gas analyzer is r = Vwhere V is the volume of the cell and the sample flow rate. 

LMTD = log mean temperature difference, °F M = mass flow rate, Ib/hr Ntu = number of heat transfer units, dimensionless N = number tubes/row in direction of air flow n = number tubes/row, per ft of exchanger width, 1 /ft Q = total exchanger heat load (duty), Btu/hr R = = heat capacity ratio, dimensionless... 

Convective heat transmission occurs within a fluid, and between a fluid and a surface, by virtue of relative movement of the fluid particles (that is, by mass transfer). Heat exchange between fluid particles in mixing and between fluid particles and a surface is by conduction. The overall rate of heat transfer in convection is, however, also dependent on the capacity of the fluid for energy storage and on its resistance to flow in mixing. The fluid properties which characterize convective heat transfer are thus thermal conductivity, specific heat capacity and dynamic viscosity. 

Providing that the flow rates are steady, the heat transfer coefficients do notvary and the specific heat capacities are constant throughout the working range, the average temperature difference over the length of the curve is given hy ... 

Considering now the case where there is a temperature gradient in the T-direction, the rate of passage of molecules through the unit plane a-a = (2 ,N (where r 2 is some fraction of the order of unity). If the temperature difference between two planes situated a distance jX apart is (0 — O ), the net heat transferred as one molecule passes in one direction and another molecule passes in the opposite direction is c,n(0 — ff), where cm is the heat capacity per molecule. 

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