File originally labelled 'Dairy heat pump and heat recovery units test data and characteristics. Mainly Bulk Tank Water'. The material includes test results for the various stages of the development of a fully integrated and reliable system of heat recovery from bulk milk Tanks. The file contains the results of lab and field work conducted at NIRD (National Institute for Research into Dairying) by ERA Foundation staff. Most items date from 1960-1968, with some later photocopies and notes added by A.S. Cromarty.