Delta T vs TD

Once again my good friend Brian Baker is keeping me honest. After my last posting  about Delta T where I said that Delta T was the same thing as Temperature Difference, Brian sent me a copy of a Sporlan Cold War Article by Garth Denison. It is essentially a refrigeration glossary of useful terms, including Delta T and TD – short for Temperature Difference. In this listing, Mr. Denison makes a distinction between Delta T and TD (temperature difference). He defines Delta T as a temperature difference between two points in the same media and TD as temperature difference between two different media. So Delta T is a temperature change in something, while TD (temperature difference) is the difference in temperature between two different things. Although the distinction is subtle, it makes some sense. Remember that the Δ symbol really stands for change. The change is represented by the change in shape of the triangle from top to bottom. In the case of a water cooled condenser, the Delta T would be the change in temperature of the water from 80°F entering the condenser to 90°F leaving the condenser. The TD, or temperature difference, would be the difference between the 90°F water leaving the condenser and the 100°F refrigerant inside the condenser.