Chapter 1, Problem 1.2DP

I- A mesurement system is to be used to mesure a presure of 250 Hz. For accurate readings, the time constant of the system sholud be (e) 0.01, (f) 1E-4, (g) 0.025. II- The bi-metallic thermometer is used to measure temperatures of --- variation. (a) very high, (b) very low, (c) above 1 Hz, (d) above 10 Hz, (e) above 100 Hz, (f) none of these. III- The static Pitot tube is suitable for measuring dynamic, (b) variable, (c) controlled, (d) directly constant, (e) dynamic, (f) constant. IV- The Borden-type gauge is a good choice to measure dynamic, (b) variable, (c) controlled, (d) directly constant, (e) dynamic, (f) static --------- sec. (a) 250, (b) 2.5, (c) 25, (d) 0.25, ---frequency fluid velocities. (a) directly pressures. (a) directly -------

A tube bank uses an aligned array with 10 mm diameter tubes and ST=SL=60 mm.    The arrangement is 10 lines of tubes with 7 tubes in each.   Cold water flows inside the tubes and their surface is kept at 30 °C, while the combustion gases flow cross-flow to the bank of tubes, the inlet temperature of the gases is 450 °C and their velocity is 15 m/s. Combustion gases can be approximated as air at 1 atm. Determine:   A) The outlet temperature of the combustion gasesB) The heat transfer coefficientC) The amount of heat transferred through the bank of tubes

Water at 10C temperature flowing from a pipe with a diameter of 100mm at a speed of 2m / s, air from a pressure of 2 ATM at 180F flowing at a speed of 50 ft / s from a pipe with a diameter of 2 in, and an oil with a specific gravity of 0.78 and a diameter of 20 cp at a speed of 5 ft / s through a 2in pipe. Shows the flow state of the biopolymer melt flowing through the pipeline at a speed of 0.2 m/s, with a density of 900 kg/m3 and a density of 1 Pa-s

A thermocouple junction of spherical form is to be used to measure the temperature of a gas stream. h = 400w/m^2 deg C; k(thermocouple junction) = 20 w/m deg C; cp = 400 J/kg deg C; and density = 8500 kg/m^3;Calculate the following:i. Junction diameter needed for the thermocouple to have the thermal time constant of one second.ii. Time required for the thermocouple junction to reach 198 deg C if junction is initially at 25 deg C and is placed in gas stream which is at 200 deg C.

The thermal boundary layer in heat transfer exists whenever there is a difference between the temperatures of the fluid and the outside environment. For fluid flow, how does a boundary layer form?A. Because common surfaces are not smooth, the flow is hindered, and boundary layers are formed.B. The disturbances on the streamlines in high Reynolds number flow produces boundary layer.C. The existence of walls or “boundaries” that keep the fluid inside (or outside) creates the boundary layer.D. Velocity profiles are inherently approaching no-slip condition because of the resistance of the walls.

19.6 In a thermal heat sink the heat flux variation along the axis of a cooling passage is approximated as 9 A TX = a + b sin (77) where x is measured along the passage axis and Lis its total length. A large installation involves a stack of plates with a 3-mm air space between them. The flow passages are 1.22 m long, and the heat flux in the plates varies according to the above equation where a = 900 W/m² and v = 2500 W/m². Air enters at 100°C

04. Airflow through a long. 0.2m square air conditioning duct maintains the outer duct surface temperature at 10 °C. If the horizontal duct is uninsulated and exposed to air at 35 °C as shown in the figure below, what is the heat gain per unit length of the duct? Air, Too-35°C NW-0.2m H=0.2 m -T₂-10°C

2, The internal diameter of a boiler generating tute is 4in. and the wall thickness is 0.375 in. In operation the external surrace film temperature is 26 Btu/hr . ft².°F, the internal film coefficient is 1700 Btu/hr.ft².°F and a 0.375 in. thickness scale having a conductivity of 0.6 Btu/hr.ft. °F is deposited on the inner surface of the tube. The metal conductivity is 26 Btu/hr.ft. °F, the furnace gas temperature is 2100 °F and the temperature of the water is 500 °F, calculate (a) the overall coefficient of heat transfer for the clean tube, (b) the overall heat transfer coefficient including the effect of the scale, (c) the external tube surface temperature before and after the scale

Using the information in Problem 1.22, estimate the ambient air temperature that could cause frostbite on a calm day on the ski slopes. 1.22 In order to prevent frostbite to skiers on chair lifts, the weather report at most ski areas gives both an air temperature and the wind-chill temperature. The air temperature is measured with a thermometer that is not affected by the wind. However, the rate of heat loss from the skier increases with wind velocity, and the wind-chill temperature is the temperature that would result in the same rate of heat loss in still air as occurs at the measured air temperature with the existing wind. Suppose that the inner temperature of a 3-mm-thick layer of skin with a thermal conductivity of 0.35W/mKis35C and the air temperature is 20C. Under calm ambient conditions the heat transfer coefficient at the outer skin surface is about 20W/m2K (see Table 1.4), but in a 40-mph wind it increases to 75W/m2K. If frostbite occurs when the skin temperature drops to about 10C, do you advise the skier to wear a face mask? What is the skin temperature drop due to the wind?