Echo removal by linear filtering - impulse response of the echo removal system - analythical solution Consider an echo removal system defined by the difference equation y[n] + ay[n – N] = x[n] In the above system, x[n] is the input signal and y[n] is the output signal. This is an echo removal system, so the input siganl, x[n], is a signal that has an echo and the output, y[n], is the signal which has the echo removed. N = 10000 and a = 0.5. Part 1. Find the impulse response of the above echo removal system (analythical solution: hand- written or typed). Part 2. Does this impulse response have a finite length or an infinite length?

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?