Boiling time

It has long been established 18 that, with scale formation, the overall coefficient of heat transfer may be expressed as a function of the boiling time by an equation of the form ... 

There are two conditions for which an optimum value of the boiling time may be sought-the time whereby the heat transferred and hence the solvent evaporated is a maximum and secondly, the time for which the cost per unit mass of solvent evaporated is a minimum. These are now considered in turn. 

The optimum value of the boiling time which gives the maximum heat transferred per cycle is obtained by differentiating equation 14.14 and equating to zero which gives ... 

The boiling time to give maximum heat transfer and hence maximum throughput is given by equation 14.15 ... 

Whilst calculated optimum cycle times may not exactly correspond to convenient operating schedules, this is not important as slight variations in the boiling times will not affect the economics greatly. 

Qb Total heat transferred during boiling time J ML2T-2... 

The boiling time is shortest in the afterchroming method, and the most level and fast colors are produced. Poor shading possibilities represent a disadvantage. The one-bath chroming method is most important. 

The optimum boiling time given by Eq. (27) shows the operating schedule necessary to permit the maximum amount of heat transfer. All the time available for operation, emptying, cleaning, and refdling should be used. For... 

The straight line CD in Fig. 11-5 starts at a distance equivalent to 6C on the left of the plot origin. The slope of this straight line is Q/(0b + 8C), with the values of Q and 6b determined by the point of intersection between line CD and curve OB. The maximum value of Q/(8b + 0C) occurs when line CD is tangent to the curve OB, and the point of tangency indicates the optimum value of the boiling time per cycle for conditions of maximum amount of heat transfer. 

CYCLE TIME FOR MINIMUM COST PER UNIT OF HEAT TRANSFER There are many different circumstances which may affect the minimum cost per unit of heat transferred in an evaporation operation. One simple and commonly occurring case will be considered. It may be assumed that an evaporation unit of fixed capacity is available, and a definite amount of feed and evaporation must be handled each day. The total cost for one cleaning and inventory charge is assumed to be constant no matter how much boiling time is used. The problem is to determine the cycle time which will permit operation at the least total cost. 

EVAPORATION OF WATFR. Prolonged boiling of fruits increases the dry matter content by evaporating water. The fruit has to boil for hours in order to achieve a sufficiently high dry matter content. This causes distinct changes in colour and taste. The shorter the boiling time, the fruitier is the jellied product. 

If the drops do not set, boiling must be continued. The maximum boiling time of about 15 min should not be exceeded, otherwise the added pectin loses its gelling power. 

A long boiling time, slow cooling and a high storage temperature are factors conducive to crystallization. The problem can be avoided by replacing part of tbe sucrose in the formulation (at least 25%) with glucose syrup. 

Sample Cure Boil Time(h) Tg°C (Before) Tg°C (After) ... 

Figures 30.18 and 30.19 show the changes in the longest water boiling time, which still pass the tape test, of primer-coated TPOs with the arc current and plasma exposure time of LPCAT treatment, respectively. From Figure 30.18 it is evident that durable bonding of the primer to TPOs was obtained with argon and methane LPCAT treatments at a lower arc current. Since the arc current represents energy input in the LPCAT process, plasma treatment conducted at a lower arc current may prevent the overtreatment on the TPO and thus give better adhesion results.

Figure 30.17 Tape adhesion test results at various water boiling times for primer on methane-plasma treated ETA-3183 with six cross-cuts made before and after immersion into boiling water 2 3 torches, 2.0 A arc current, 1000 seem argon, 10 seem methane, 270mtorr pressure, and 1.9 s plasma exposure time.

Figure 30.18 The effects of plasma treatment arc current on the water boiling time, which pass the tape test, of primer-coated ETA-3183 specimens 2 3 torches, 1000 seem argon, 10 seem air, 270mtorr pressure, and 12.3 s plasma exposure time (1.9 s for methane plasma).

Figure 2. Influence of sample preparation time on apparent heterogeneity. pMAB and hAB-1 were mixed with non-reducing SDS-PAGE sample buffer and boiled for various times prior to electrophoresis. Boiling times Lanes 1,2 1 minute, lanes 3,4 5 minutes and lanes 5,6 10 minutes. Samples pMAB (lanes 1,3 and 5), hAB-1 (lanes 2,4 and 6).

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