Three types of Direct Contact, High Capacity Steam Heaters are available to meet critical application requirements.
The Fig. 326 Direct Contact, High Capacity, Multi-Spray Steam Heater is suitable for very large quantities of hot water, a top vapor inlet is required, and steam pressure is atmospheric or above. Water is distributed peripherally to a series of converging spray nozzles which disperse the inlet water into very fine particles. Further dispersion is accomplished by a centrally placed deflection baffle. Steam enters at the top and passes through the water spray, condensing immediately and completely. The hot water is delivered to a tank through an outlet at the bottom of the heater. If internal pressure is below atmospheric pressure, a barometric leg, long enough to balance the pressure within the heater must be used to permit discharge of the hot water. The air vent prevents accumulation of non-condensables and balances the pressure of the heater.
Fig. 337 and Fig. 338 Direct Contact, High Capacity, Counter-Current Heaters are “counter-current” types with the water and steam flowing in opposite (counter) directions. All operate effectively with internal pressures above and below atmospheric pressure. With typical units of medium size, hot water capacities range from 6 to 6,000 gpm. No limits on unit size have been set and, since capacities are determined by unit size and steam available, there are no limitations on hot water capacity. In conventional units, a water temperature rise of 130ºF is obtainable provided air is absent and other operating criteria are met. In the Counter-Current Heater, water sprayed in from the top comes in direct contact with steam entering the vapor inlet. The resulting heated water discharges through the bottom hot water discharge connection. Any non-condensables can be vented through the vent connection adjacent the water inlet.
The Fig. 323 Direct Contact, High Capacity, Continuous Heater is suitable for operation within a wide range of conditions. It does not require a barometric leg. At atmospheric pressure and above, a temperature rise of 100ºF is obtainable. Hot water capacity ranges from 10 gpm to 240 gpm. The Type 323 Heater should not be used if air and other non-condensables are present.
The Fig. 326 Direct Contact, High Capacity, Multi-Spray Steam Heater is simple in design, having no moving parts. Heating is continuous and fast. Inspection and routine maintenance are greatly facilitated by conveniently placed access ports. Because of high heating efficiency, a relatively small, lightweight size can be used to deliver a large supply of heated liquid. Heat transfer in direct contact heaters is better than shell and tube heaters because heat transfer resistances like film, fouling, and wall, are not present. Since heat transfer is more effective, a small direct contact heater can be used thereby minimizing cost. Maintenance is low when compared with costly shutdowns needed to clean tube bundles, that act like strainers, when tube pitch is sacrificed for surface area in shell and tube heat exchangers.
Fig. 337 and Fig. 338 Direct Contact, High Capacity, Counter-Current Heaters have no moving parts, give fast continuous heating, are easy to install, and can be supplied at low cost in corrosion-resistant materials. Heat transfer in direct contact heaters is better than shell and tube heaters because heat transfer resistances like film, fouling, and wall, are not present. Since heat transfer is more effective, a small direct contact heater can be used thereby minimizing cost. Maintenance is low when compared with costly shutdowns needed to clean tube bundles, that act like strainers, when tube pitch is sacrificed for surface area in shell and tube heat exchangers.
Fig. 323 Direct Contact, High Capacity, Continuous Heaters are inline and therefore, require no containment vessels. These heaters can supply hot water at low levels requiring no barometric legs when the steam is below atmospheric pressure. Shell and tube heaters in the same application need auxiliary pumping equipment or barometric legs to drain condensate under vacuum. Fixed nozzle continuous heaters have no moving parts, are easy to install, require little or no maintenance, mix as well as heat, and give complete heat exchange.