December 8, 2019

Why cool the water (part 1)

Water is a precious commodity. Spoiling water is not only a waste of money, it also destroys a natural resource that is otherwise beneficial to all of us. Without saving water, irrigation and drinking water sources will be compromised. 

Machinery, labor, efficiency, and energy scrap to dispose of.

Today, machines are used to produce goods that help us to live a better life and to manufacture a whole range of products. 

Machines use energy to transform work into products. Not all of the energy used will be transformed into work; part of it will be dispersed in various forms such as friction and, in any case, heat. 
Hence, heat is energy scrap and its amount depends on the efficiency of the machine.

Water as a means of transporting energy as heat.

The heat transmitted from machines that is no longer used, must be dispersed. And, the first think that comes to mind is to use air as a cooling element. However, if you think about it, it would take an enormous quantity of air to cool industrial machines such as welders, chemical reactors, or even a machine for molding plastics. Another element available in nature and much more effective than air is water. The specific heat, the ability to "hold" the heat, make it such that water is much more convenient to use it as a mean of transporting intense heat, that is, scrap energy from operating machines.

Need to recycle the water.

Water heats up when used to cool machines. If the same water is used again to cool the same machine, at the end of the second cycle the water will be even hotter than before. After several cycles the water temperature equals to that of the machine, therefore heat transporting will be no longer beneficial. This is because after a period of time, more or less long, the water and the machine will have the same temperature. At this point, the machine can no longer expel the heat and its efficiency will decrease dramatically up to the point where it will fatally block production, for which the machine itself was intended to operate. 
Hence, the need to throw away hot water and use fresh water. But, is it better to use fresh water in a squanderly way or reuse the same hot water coming out of the machine that is cooled down and put it back into the circuit.

Examples of amounts of water needed in manufacturing plant. 

Energy performance in manufacturing machines is unfortunately very low. In some cases machine performance can be around 70%, but most machines perform below 50%. This means that the majority of energy must be disposed as heat. If the heat is disposed with water, then the water is either thrown away or put back into the circuit. Throwing it all away would be a big waste. 

Let's try to calculate how many people consume the same water in a small plastic molding plan:

a) a plastics molding plant that employs 20-30 people, needs 40 cubic meters per hour of water, or more than 40,000 liters per hour, equivalent to 40,000 x 24h = 960,000 liters per day, to cool its machines.

b) a person in a well-being environment consumes 250 liters of water per day.

The result is that an average small-medium size plant consumes as much as a country of 3,840 inhabitants.

Other examples can apply to steel plants, oil refineries, cold storage and any other manufacturing plant.