Instantaneous water heaters

The first instantaneous water heaters which started appearing in the 1890s when gas or liquid fuels started becoming available, were un-pressurized. The first models had no automatic controls and vei"y limited safety features. Some early models were more efficient than standard modern gas-fired water heaters. 

Early in the twentieth centui y over 150 different manufacturers were making storage tank, instantaneous, and solar water heaters. Then as indoor plumbing became more common and as people started using showers more and baths less, storage type water heaters became more popular. Accurate hot water temperatures were not possible in early instantaneous water heaters. This was not much of a prob-... 

Outside of the United States and Canada, storage water heaters are common in Australia, Southern Africa, Latin America, and Britain. Instantaneous water heaters are much more common particularly in Asia and Europe. In countries that were once part of the British Empire, unpressurized storage tanks that relied on gravity were common, however most have changed over to pressurized storage tanks. 

Electric storage hot water heaters and instantaneous water heaters are used for simple domestic applications and are not considered in this text. For many smaller HW and lower pressure steam generation applications (including bakery ovens and proofers, jacketed kettles, fish pots and other cooking equipment, wineries, breweries, textiles, laundries, phosphatizing processes, humidification, steam baths, clean rooms, and pharmaceuticals), electric boilers offer significant advantages over fossil-fuel boilers and are often the product of choice. 

Instantaneous water heaters, i.e. where the element is in contact with the water, again need additional earthing by bonding the metal water supply pipe to the main earthing terminal see section 554-05. Supplementary equipo-tential bonding will also be needed if the heater is in a bathroom or shower cubicle see section 601. 

Introducing the only commercial size instantaneous water heater above 250,000 BTU/HR. 

Pressure regulators have been successfully used as cascade slaves receiving their set points from temperature control masters. Figure 3.147 illustrates such an installation on a steam-heated water heater. This configuration works well, because the air-loaded pressure regulator is extremely fast and corrects for load changes or steam-supply pressure variations instantaneously. 

Recommendation. Replace the existing hot water heater with an instantaneous hot water heater to be installed in the men s bathroom fed from the existing piping. 

Figure 6.3. Levitation of a molten metal in a radio-frequency field. The coil consists of water-cooled copper tubes. The counter winding above the sample stabilizes levitation. The same coils (and possibly additional ones) act as the induction heater. This technique has been applied to container-less melting and zone refining of metals and for drop calorimetry of liquid metals. It can be also used to decarburize and degas in ultrahigh vacuum mono-crystalline spheres of highly refractory metals (adapted from Brandt (1989)). The arrows indicate the instantaneous current flow directions in the inductors.

Continuous Starch Hydrolysis. A commercial continuous converter installation for dextrose manufacture employing a continuous, automatically controlled step for the hydrolysis of starch is now in operation. A flow diagram of a modem commercial installation for continuous starch hydrolysis is shown in Fig. 13-4. The starch converter consists of an 8-in. coil, 677 ft long, which is fed by a high-pressure centrifugal pump from a continuous starch make-up tank equipped for automatic control of density (Baumd), level, and acidity. The level controller regulates the addition of 20 B starch suspension, the Baum controller operates the water valve, and a conductivity instrument controls the addition of acid. The head end of the converter coil has an entry chamber to separate non-condensables, and the feed is instantaneously heated with live steam through a jet heater. 

Also included in Fig. 23 are Bonilla s data (B9a) for nucleate boiling of pentane from a chrome-plated heater, as well as the average over all heat-transfer coefficient, related to the instantaneous overall heat-transfer area, for pentane drops evaporating while rising in water. As noted earlier, the heat-transfer coefficient in the latter case was found to be practically independent of the temperature driving-force in the range studied (up to 15°C). 

An auxiliary heat source can also be installed as an after-heater. The solar part of the system would thus become a preheater. Only when draw-off occurs would the solar-heated water flow into the after-heater, at whatever the temperature it is, and be brought up to the required temperature level. This after-heater may be a flow-through-type (instantaneous) or a storage-type device. Under favorable conditions it may not be called on to operate, but it would serve as a standby unit. Table II shows a classification of solar DHW systems according to seven attributes. 

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