A 3-phase transformer is assembled by connecting three 85-kVA, 110kV/15kV, single-phase transformers. The primary is connected in delta and the secondary is connected in Y. 1) Draw the winding arrangements of the 3-phase transformer 2) Determine the nominal voltages and power rating of the 3-phase transformer.

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?

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

Modern high speed trains do not have perpendicular expansion gaps where rails are joined end-to-end any more they are mostly welded together but what might happen if there was a spell of particularly hot weather that causes inspection of the tracks?