Que es el control como un sistema de retroalimentacion

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?

Describe one experiment in which the glass transition temperature and melting temperature of a totally amorphous thermoplastic material can be determined. show the relevant experimental results in a diagram which should be properly annotated with the two temperatures clearly marked. what is likely to happen to the curve in the diagram if the amorphous polymer is replaced by a thermosetting type?

Atank with constant volume contains 2.27 kg of a mixture of water phases (liquid-vapor). in the initial state the temperature and the quality are 127 °c and 0.6, respectively. the mixture is heated until the temperature of 160 oc is reached. illustrate the process in a t-v diagram. then, determine (1) the mass of the vapor in kg at the initial state, (2) the final pressure in kpa.