GB1488563A - Evaporative cooling method using natural circulation of cooling water - Google Patents

Abstract

1488563 Furnace cooling systems; boilers NIPPON KOKAN KK 2 May 1975 [20 May 1974 27 Sept 1974] 18362/75 Headings F4B F4A and F4U In a method of cooling apparatus such as a furnace 3 using a natural circulation evaporative cooling system comprising a steam separator drum 1, a downcomer 2, a cooling pipe 4 and a riser 5, with the amount of make-up cooling water added to the system corresponding to the quantity of steam generated within the system and discharged from the separator drum 1 through a line 10, the cooling water in the cooling pipe 4 is maintained in a completely liquid state, with evaporation of part of said cooling water taking place only in said riser 5 and said steam separator drum 1, by selecting system parameters to satisfy the following formula where Q = thermal load acting on the cooling pipe, V = amount of cooling water circulating in the cooling pipe, # = density of the cooling water, c=specific heat of the cooling water, P h3 =pressure of cooling water in the uppermost part of the cooling pipe, P 0 =pressure in the separator drum, and #T eg (P 0 ,P h3 ) = the boiling equilibrium temperature difference between P 0 and P h3 and wherein at least part of the makeup cooling water is introduced into the downcomer 2 of the system. The cooling system additionally includes downcomer and riser headers 7 and 8, thermometers 15 and 16, and manometers 13 and 14. As shown the make-up water is wholly introduced into an auxiliary drum (17, Fig. 4, not shown) in the middle of the downcomer 2. Alternatively part may be introduced into the main drum 1 and part into the auxiliary drum (17 see Fig. 4, not shown); the proportion supplied to each may be regulated in dependence of vapour volume measuring devices (20A, 20B) located at different levels in the riser 5. Alternatively, as shown in Fig. 5, the cooling water may be made-up continuously by sensing any deviation of the water level within the main drum 1 from a predetermined value and accordingly selectively adding make-up water to the main and/or auxiliary drums 1 and 17. The amount of water to be replenished is measured by a steam flow meter 21, and the measured value, together with the difference between the actual level of water in the drum 1 and the predetermined level, as measured by a pressure gauge 22, is fed into a programmer unit 23; actuating signals are then fed to a water feed valve 11 and/or a supplementary valve 18. When a plurality of cooling pipes are used (see Fig. 7, not shown), to ensure that the cooling water is maintained in a liquid state in all of the pipes, each pipe is provided with a flow rate regulating valve (24) at its inlet end and a temperature sensor (25) at its outlet end, the flow rate of cooling water in each of the pipes being adjusted in dependence of the measured outlet temperature, so that all the outlet temperatures of cooling water in said pipes are equal.