tube-tube heat exchanger / liquid/liquid
The sludge heat exchanger is installed when it is necessary to keep the operating temperature of the sludge digester constant in order to avoid any sudden thermal changes higher than 2 or 3 °C. The exchanger consists of a set of concentric pipes joined with 180° elbows. The sludge circulates in the internal piping, while the water runs externally, reverse current with respect to the sludge stream, and has a heat flywheel function. The inlet sludge temperature is about 30-32 °C, while that of the outlet sludge is 37-40 °C. The sludge speed inside the exchanger is about 1.5 m/s.
The maximum heat exchange capability is about 22.500 kcal/m2xh.
A vent valve and an exhaust valve in correspondence of the top and bottom sections of pipings assure the maximum efficiency. The exchanger is completely demountable to allow pipes easier internal cleaning operations.
The standard construction is in carbon steel. On request it is possible the realization in stainless steel for all the parts or the construction of models with internal tubes in stainless steel and external tubes in carbon steel.