The issue of the expansion tank in an open-loop heating system also serving as a heat exchange tank
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I would like to ask my colleagues: Our company has a small heat exchange station that uses an open mechanical circulation system for heating. The water supply pump has a flow rate of 50 m3/h and a head of 50 meters; the motor driving it has a power of 11 kW. The expansion tank has a capacity of 1.1 m3, and steam is introduced into this tank to heat the water as well. Due to the large area that needs to be heated, the radiators do not get hot enough. Apart from increasing the amount of steam used to raise the water temperature, could increasing the capacity of the expansion tank help? The questions are as follows: (1) Is there an issue with the heat exchange rate when steam exchanges heat directly with heating water, that is, could increasing the steam consumption lead to the steam escaping before it has enough time to exchange heat with the water? (2) What determines the capacity of a heating water tank? Does it have a \"heat storage\" function? In other words, can it be understood that it takes some time for the heating water to flow through the system, during which time steam first heats the water stored in the tank before it is supplied; and once the return water from heating comes back to the tank, it is heated again before being supplied outside?
(1) Is there an issue with the heat exchange rate when steam exchanges heat directly with heating water? In other words, could increasing the steam consumption lead to the steam escaping before it has enough time to exchange heat with the water? The direct steam method is naturally the fastest way for heat transfer; since there’s no time for heat exchange before the steam escapes, it’s necessary to use steam inlet distribution pipes. If steam is introduced directly into the water through a single pipe, the efficiency of steam utilization will definitely be much lower. (2) What determines the capacity of a heating water tank? Does it have a \"heat storage\" function? In other words, can it be understood that it takes some time for the heating water to flow through the system, during which time steam first heats the water stored in the tank before it is supplied; and once the return water from heating comes back to the tank, it is heated again before being supplied outside? It is necessary to perform a heat balance analysis, considering the heat provided by steam, as well as the heat exchange and losses within the system, in order to identify the key factors involved in solving the problem. By determining the required temperature of the heat exchange surfaces, it becomes possible to calculate the amount of heat that needs to be supplied for heating and the measures required for insulation.