Heat Exchangers for District Heating Substations and Networks

District heating distributes hot water from a central plant to many buildings through a primary network at 90–120 °C and 16–25 bar. Each building takes heat from the network via a substation that isolates the primary network from the building's secondary heating and domestic hot water loops. Plate heat exchangers are the default choice for substations because of their high efficiency, close temperature approach, compact footprint, and ease of cleaning and gasket replacement over a 20–30 year service life.

A typical building substation has two heat exchangers: one for space heating (primary to secondary heating water) and one for domestic hot water (primary to mains water through a tap-water-grade plate pack). The heating exchanger is sized for the building peak heat demand; the DHW exchanger is sized for instantaneous tap demand, typically using high-theta plates for close approach and fast response.

Stainless 316L plates with EPDM gaskets are standard for both primary and secondary loops in clean district-heating water. Domestic hot water side uses EPDM peroxide-cured gaskets that comply with drinking-water regulations. Where the primary network has elevated chlorides or chemistry uncertainties, 254 SMO is sometimes specified for the primary side as a precaution.

Modern fourth-generation district heating networks operate at lower supply temperatures (50–70 °C) to integrate heat pumps, waste heat and renewables. Lower supply temperature requires larger heat transfer area for the same building duty — typically 30–60% more plate area than legacy 120 °C networks. Plate heat exchangers with low-theta high-area plates are the right selection for this segment.

Primary-side design pressure for district heating substations is typically 16 or 25 bar with 110–130 °C design temperature. PED certification is required across the EU; national equivalents apply elsewhere. Hydrostatic test at 1.43× design pressure is standard. Specify the design code and pressure class at inquiry — re-certifying a unit after delivery is expensive.

District heating substations are inspected on a 5–10 year cycle, with gasket replacement and plate cleaning as the main maintenance items. Plate heat exchangers in district heating service routinely reach 25–30 years of service when maintained on schedule. Jiangxing supplies primary, secondary and DHW exchangers for district heating projects worldwide, with engineered selections and full code certification.