Heat exchangers grow green

Manchester, UK -- Netherlands-based specialist Van Dijk Heating is using Tranter International AB’s plate heat exchangers (PHE) in its greenhouse water disinfection equipment. The design, claims Tranter, is providing substantial energy savings for flowers, fruit and vegetable growers around the world.

The Dutch firm’s Ecoster drain water disinfector is used to disinfect the drainage water from the greenhouses - and remove fungi, bacteria and viruses - prior to its re-use. The disinfected water contains valuable fertilisers, which would otherwise have to be flushed away and disposed of.

Using this equipment, cost savings of up to 50% on fertilizers have been recorded, depending on the drain percentage and the exact nature of the crop, according to Tranter.

Van Dijk manufactures two types of disinfector unit; one which has an integral gas burner and a second which is linked to an existing source of energy such as a heating circuit via another heat exchanger. After the disinfection process, the water is quickly cooled and passed into a holding tank for re-use.

The Tranter PHE provides the means by which this cooling is achieved, taking heat from heat and channelling it into the early stage of the process to save energy and maximise the overall efficiency of the plant.

Disinfection is based on a simple heating principle and takes place in a continuous process. The incoming water is quickly heated from around 20 °C to 95 °C and maintained at this temperature for 40 seconds. Complete disinfection is guaranteed by a sophisticated computer-based temperature control system.

Within the system, the heat exchanger raises the temperature of the disinfector’s 20 °C intake water by as much as 70 °C and requires the gas burner or additional heat exchanger to ‘add’ only another 5 °C.

The PHEs “give us the energy efficiency, performance, compactness and reliability that we require, coupled with a highly service-oriented and problem-solving approach,” said Nico de Bruin of Van Dijk Heating.