Cool down large mass

The setting of concrete is an exothermic reaction, and large masses of concrete in building foundations, bridges and dams will heat up, causing expansion cracks if not checked. To counteract this heating, the materials are cooled before and as they are mixed, so that the concrete is laid some 15 K colder than ambient, and warms to ambient on setting. In practice, the final mix temperature can be held down to 10°C. 

Another assumption we made—that all collisions with the wall are elastic and transfer no energy because of the large mass difference—may strike you as quite strange if you think about it carefully. Heat transfer between gases and solids is readily observed. The air in your refrigerator will cool down food the air in your oven will heat it. 

In missile-loading and certain other transfer systems, large quantities of cryogenic liquids must be transferred in a relatively short time. Such systems must be cooled to the point at which transfer is accomplished as a liquid rather than as a gas in a fraction of a minute, or, at most, in a few nqiinutes. Four significant factors influence the cool-down time of a transfer system (1) transfer pressure (2) heat leak to the fluid from the environment (3) line flow impedance and (4) quantity of system mass that requires cooling. These factors have been studied experimentally by Burke et al., who have developed an equation for predicting cool-down times of horizontal lines. 

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