Cooling mode

Batch Crystallization. Crystal size distributions obtained from batch crystallizers are affected by the mode used to generate supersaturation and the rate at which supersaturation is generated. For example, in a cooling mode there are several avenues that can be followed in reducing the temperature of the batch system, and the same can be said for the generation of supersaturation by evaporation or by addition of a nonsolvent or precipitant. The complexity of a batch operation can be ihustrated by considering the summaries of seeded and unseeded operations shown in Figure 19. 

In operating a coohng tower in the thermocycle or free-cooling mode, some precautions are necessary to minimize icing problems. These include fan reversals to circulate air down through the tower inlet louvers, proper water distribution, constant water flow over the tower, heat tracing of lines such as makeup lines as required, and maximum loading per tower cell. 

Chemical heat pump uses chemical reaction for thermal energy storage and conversion. The heat pump operation is based on reaction equilibrium relationship, and has two operation modes. Figure 221 shows equilibrium relationship of chemical heat pump cycle for Mg0/H20 system at (a) heat amplification and cooling mode and (b) heat transformation mode [26], Figure 222 shows... 

Figure 221. Equilibrium relationship of chemical heat pump cycle for MgO/EFO system (a) heat amplification and cooling mode, (b) heat transformation mode...

S. M. Sarge, G. W. H. Holme, H. K. Cammenga, W. Eysel, E. Gmelin. Temperature, Heat and Heat Flow Rate Calibration of Differential Scanning Calorimeters in the Cooling Mode. Thermochim. Acta 2000, 361, 1-20. 

The forced-circulation crystallizer is a simple unit designed to provide high heat-transfer coefficients in either an evaporative or a cooling mode. Figure 12 shows a... 

If a cooling mode is used to generate supersaturation, an analysis similar to that given above can be used to derive... 

Equipment Mode 1 (Mechanical refrigeration) Mode 2 (Vapor migration based indirect free cooling) Mode 3 (Indirect free cooling by the use of heat exchanger) Mode 4 (Direct free cooling with full filtering)... 

Bashir et al. (1998), in a study of phase transitions in a monotropic liquid-crystal polyester, found that PC and HF instruments performed differently in cooling mode. Better resolution of thermal events (i.e., better separation of peaks on the thermogram) was obtained with PC instruments. These authors pointed out that the performance of any DSC instrument might not be the same during heating as during cooling. 

The considered experimented set - up can be applied in two different ways. The first one is to use is as a semiconductor sensor cooler with low heat dissipation to cool the sensor down to the ambient temperature. It is interesting to be applied in cryogenic range of temperatures. The second option is related with the cooler for high energy dissipation devices (for example laser diode cooler). The first set of experiments was performed with sorption heat pipe and ammonia as a working fluid to demonstrate the basic possibility to decrease the temperature of the heat loaded wall to compare with the temperature of this wall in the phase of loop heat pipe cooling mode. 

Sarge, S.M. Hohne, G.W.H. Cammenga, H.K. Eysel, W. Gmehn, E. Temperature, heat and heat flow rate calibration of scanning calorimeters in the cooling mode. Thermochim. Acta 2000, 361, 1-20. 

On the other hand, assuming the cooling mode of the fluid to be Newtonian, the quantity of heat transferred per unit time from the fluid, through the whole fluid surface, across the container walls, to the atmosphere, q2, is expressed as... 

Figure 28 Structure of [Fe(btr)2(NCS)2] H20 and xmT versus T curves in the wanning and cooling modes for this compound. Reproduced with permission from ref. 100.

In the cooling mode, supersaturation can be efficiently controlled using readily available solubility data as a function of temperature. 

FIGURE 18.4 Different cooling modes dotted line = natural cooling dashed line = programmed cooling middle line = linear cooling. 

The fables below give the values of those properties (read from the pressure-enthalp) diagram) at each point in the cycle needed for the calculation of the coefficient of performance in the heating and cooling modes of the heat pump. In the.se tables the propertie known at each point from the problem statement or from an adjacent point appear in boldface, and the properties found from the chart at each point appear in italics. 

Note that in both the heating and cooling modes, the heat pump in thi.s illustration has a lower coefficient of performance (and therefore lower efficiency) than a reverse Carnot cycle operating between the same temperatures. Finally, it should be mentioned that the thermodynamic properties listed above were obtained from a detailed thennody-naniic properties table for HFC-134a, akin to the steam tables for water in. < ppendix A.Ill values cannot be obtained from Fig. 3.3-4 to this level of accuracy. ffl... 

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