What is delta T?

[@normanboyes4983]

Actually, there is no universal application of ‘Delta T’ in essence it means the difference between the two temperatures under consideration. For example radiator output is often specified at specific ‘Delta Ts’ which is the difference between the mean radiator temp and the desired room temperature, Heat exchangers in boilers are often referred by their Delta T the difference between the flow and return temp ( or the temp rise across the boiler). In Sum, Delta T just refers to temperature difference - the application however can be specific - if it is specified.😉