Run all around coil: comprises two or even more multi-row finned tube coils linked to each other by a pumped pipework circuit. Thermal wheel or rotary heat exchanger: is made up of a round honeycomb matrix of heat absorbing substance, which can be slowly rotated in the supply and exhaust https://purethermal.co.uk/media-news/november-launch-waste-heat-recycling-design-support-service-from-pure-thermal-and-oilon/