Calculate values for the Fermi function f(E) at 300 K and plot vs. energy in eV as in Fig. 3–14. Choose EF = 1 eV and make the calculated points closer together near the Fermi level to obtain a smooth curve. Notice that f(E) varies quite rapidly within a few kT of EF. Show that the probability that a state ΔE above EF is occupied is the same as the probability that the state ΔE below EF is empty

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?