For hot water systems, using indirect heat exchangers in place of direct injection based systems is beneficial.
The traditional method of hot water generation has been by direct injection of steam into a hot water tank. There are some inherent gaps in this method of hot water generation.
At plants that have closed loop hot water system, with such systems, overflow of hot water from the tanks is a common problem. This is because though the intention of injecting steam is for temperature rise, steam injection also adds mass. In most conventional systems the injection of steam is in the absence of precise control of temperature which usually leads to temperature overshoot and thus increased steam consumption. Usually there is improper mixing of water and steam leading to non uniform temperature profiles. Also in these systems the tanks hold a huge quantity of heated water. Hence the associated radiation loss is high.
Modern steam systems, using a plate type heat exchanger to raise the temperature of the hot water in an instantaneous hot water generation system, solve these problems. This system of hot water generation delivers:
- Precise Control of temperature
- No overflows –thus reduced steam & water consumption
- Reduced radiation losses
- Recovery of condensate to boiler house.
Consider a hot water requirement of 10KL/hr at a temperature of 80 degC and a water return temperature of 70degC. Considering a 3 degC over shoot, steam is used to heat the water from 70 degC to 83degC. Thus ,