Green's Power | Economisers, waste heat boilers, land & marine boilers, steam air heaters & other pressure parts Heat Exchange Group is the leading UK and worldwide supplier of the widest range of heat exchanger and industrial/marine boiler products and services.The Group was formed in 2018, following the merger Heat Exchange Group is the leading UK and worldwide supplier of the widest range of heat exchanger and industrial/marine boiler products and services.The Group was formed in 2018, following the merger of Green’s Power and Thornhill Heat Exchangers. In 2022 Heat Exchange Group acquired the skilled team members, drawings and intellectual property of Hunt Thermal Technologies, owner of the Johnson Hunt, Hunt Graham and Wellman brands, further bolstering its specialist heat exchanger offering.