Xác định vùng bảo vệ của hai cột thu sét kép có cùng chiều cao 21m một khoảng 7.4m theo bề rộng. Kiểm tra xem thiết bị có được an toàn hay không.

Apipe with an outside diameter of 15 cm is exposed to an ambient air and surrounding temperature of -20°c. the pipe has an outer surface temperature of 65°c and an emissivity of 0.85. if the rate of heat loss from the pipe surface is 0.95 kw per meter of length, the external convective heat transfer coefficient (h) is: (a) 12.5 w/m"k (b) 18.6 w/mk (c) 23.7 w/mk (d) 27.9 w/mk (e) 33.5 w/mk

Acompressor compresses a gas, a pump compresses a liquid. for a given pressure ratio, why does it take more work to compress a gas in a compressor than a liquid in a pump? a)- for a given pressure ratio the average specific volume for a gas is much higher than the average specific volume for a liquid. b)- there is no difference. the only difference is the amount of heat generated (not work) c)- for a given pressure ratio the average volurge for a gas is much higher than the average volume for a liquid. d)-there is no difference

Cold water (cp=4180j/kg k) leadıng to a shower enters a thin-walled double-pipe heat transfer at 15c at a rate of 0.25kg/s and is heated to 45c by hot water (cp=4190j/kg k) that enters at 100c at the rate of 3kg/s. if the overall heat transfer coefficient is 950w /m2 k , determıne the rate of heat transfer and the heat transfer surface area of the heat exchanger using e - ntu method