V O L . 7 , D O C . 6 0 a C A L C U L A T I O N S O N C O O L E R 2 1 Vol. 7, 56b. Professor Einstein on the Proposed Hebrew University of Jerusalem [before 3 April 1921][1] [See documentary edition for English text.] Vol. 7, 60a. Calculations on a Cooler [July 1921– March 1922][1] Given to Mr. Müller & Nernst[2] In isothermal compression there must be supplied: 1) work 2) heat . Hence . The negative thereof is the total energy (per unit mass of the working fluid[4] ) discharged from the compressor, therefore, according to the equation of energy, also the heat extracted or cold discharged from the other component, if the effect of heat conduc- tion between exchanger and compressor is neglected, which is not always permissible. (If heat flows from exchanger to compressor, then the amount of heat discharged outwards by the latter is con- served, that is, also the cold discharged by the other component.) If one ignores this, then . According to the second law, hence also and [3] A –pν p Δp) + ( ν Δν) + ( pΔν – + νΔp = = W Δu pΔν += A W + Δ( u pν) + = K A W) + –( ∂u ∂p ----- -– ν – p----- ∂ν ∂p - – Δp = = ∂u ∂p ----- -– p----- ∂ν ∂p - – T------ ∂ν ∂T = K T------ ∂ν ∂T ν – Δp =