We know that water freezes at 0º C, i.e. 273K is the freezing point of water at atmospheric pressure. So in the areas where the atmospheric temperature is cold, in the range of -3ºC, still the liquid water flows from the shower nozzle. Ever wondered how is that possible?
There is no heater, water pump, or any super-cool technology involved in this phenomenon, rather simple, and basic science is applied. We know that as water starts cooling, at 4ºC, it starts expanding. Now think that if the expansion is constrained by strong pipes and water is made to flow drop-by-drop in the shower tap. This water has no possibility of expansion and hence it doesn't cool down to freezing temperature. Thus, people can take showers in sub-zero temperatures too.
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