Flow rate heat transfer

The 3 most important design parameters for a twin-screw are shown in Fig. 5. For more accurate scale-up from lab tests to the production machine they should be kept constant within an extruder series. Additionally operating parameters such as specific heat transfer, flow-rate per die and vapor velocity in the vacuum zone should remain constant as well. 

F jure 11.9 depicts the idea of thermal resistance and how it is related to the material s thickness, area, and thermal conductivity. When examinii Equation (11.13), you should note the following (1) The heat transfer (flow) rate is direedy proportional to the temperature difference (2) the heat flow rate is inversely proportional to the thermal resistance—the hi er the value of thermal resistance, the lower the heat transfer rate will be. 

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... 

In addition to impurities, other factors such as fluid flow and heat transfer often exert an important influence in practice. Fluid flow accentuates the effects of impurities by increasing their rate of transport to the corroding surface and may in some cases hinder the formation of (or even remove) protective films, e.g. nickel in HF. In conditions of heat transfer the rate of corrosion is more likely to be governed by the effective temperature of the metal surface than by that of the solution. When the metal is hotter than the acidic solution corrosion is likely to be greater than that experienced by a similar combination under isothermal conditions. The increase in corrosion that may arise through the heat transfer effect can be particularly serious with any metal or alloy that owes its corrosion resistance to passivity, since it appears that passivity breaks down rather suddenly above a critical temperature, which, however, in turn depends on the composition and concentration of the acid. If the breakdown of passivity is only partial, pitting may develop or corrosion may become localised at hot spots if, however, passivity fails completely, more or less uniform corrosion is likely to occur. 

During the time an evaporator is in operation, solids often deposit on the heat-transfer surfaces, forming a scale. The continuous formation of the scale causes a gradual increase in the resistance to the flow of heat and, consequently, a reduction in the rate of heat transfer and rate of evaporation if the same temperature-difference driving forces are maintained. Under these conditions, the evaporation unit must be shut down and cleaned after an optimum operation time, and the cycle is then repeated. 

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... 

A = heat transfer surface c = specific heat of batch liquid = heating medium specific heat M = weight of batch liquid T, = heating medium temperature t = initial batch temperature t2 = final batch temperature U = overall heat transfer coefficient = batch flow rate - heating medium flow rate 0 = time... 

U = overall heat transfer coefficient Wt, = batch flow rate. = heating medium flow rate... 

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. 

HEAT TRANSFER. In Fig. 4, typical local values of the heat-transfer coefficient h are plotted as a function of the test-section length for various mass-flow rates and heat inputs. The heat fluxes, flow rates and inlet conditions are tabulated on the figure. 

Film Coefficient (1) In convective heat transfer, the rate of heat flow through a stagnant fluid film adjacent to a solid surface, per unit area of the film, divided by the... 

To evaluate the cladding temperatures directly during abnormal transients, it was necessary to develop a database of heat transfer coefficients at various conditions of heat flux, flow rate, and coolant enthalpy. The database of heat transfer coefficients was prepared by numerical simulations that successfully analyzed the deterioration phenomenon itself. The database, Oka-Koshizuka correlation, has been used for safety analysis. 

Because the characteristic of tubular reactors approximates plug-flow, they are used if careful control of residence time is important, as in the case where there are multiple reactions in series. High surface area to volume ratios are possible, which is an advantage if high rates of heat transfer are required. It is sometimes possible to approach isothermal conditions or a predetermined temperature profile by careful design of the heat transfer arrangements. 

Thus loops, utility paths, and stream splits offer the degrees of freedom for manipulating the network cost. The problem is one of multivariable nonlinear optimization. The constraints are only those of feasible heat transfer positive temperature difference and nonnegative heat duty for each exchanger. Furthermore, if stream splits exist, then positive bremch flow rates are additional constraints. 

In the Couette flow inside a cone-and-plate viscometer the circumferential velocity at any given radial position is approximately a linear function of the vertical coordinate. Therefore the shear rate corresponding to this component is almost constant. The heat generation term in Equation (5.25) is hence nearly constant. Furthermore, in uniform Couette regime the convection term is also zero and all of the heat transfer is due to conduction. For very large conductivity coefficients the heat conduction will be very fast and the temperature profile will... 

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