FYKOS Year 34 Series 2 Problem 4 — lifting ice using heat · FYKOS 34 #34.2.4

Physics · thermodynamics

Problem

A man stores small ice blocks in a well

h = 4.2\,\mathrm{m}

deep. To lift the ice up, he uses a heat engine between ice and the surrounding air with efficiency

\eta=12\%

of the respective Carnot engine. The temperature of available air is

T_{\mathrm{air}}=24\,\mathrm{^\circ\mskip-2mu\mathup{C}}

. How cold must the ice be at the beggining in order to retrieve it with a final temperature

T_{\mathrm{max}}=-9\,\mathrm{^\circ\mskip-2mu\mathup{C}}

? How is it possible even when we heat the ice up in the process?