Aheating cable is embedded in a concrete slab for snow melting. the heating cable is heated electrically with joule heating to provide the concrete slab with a uniform heat of 1200 w/ m2. the concrete has a thermal conductivity of 1.4 w/m⋅k. to minimize thermal stress in the concrete, the temperature difference between the heater surface (t1) and the slab surface (t2) should not exceed 16°c (2015 ashrae handbook—hvac applications, chapter. 51). formulate the temperature profile in the concrete slab, and determine the thickness of the concrete slab (l) so that t1 − t2 ≤ 16°c.

Amass of m 1.5 kg of steam is contained in a closed rigid container. initially the pressure and temperature of the steam are: p 1.5 mpa and t 240°c (superheated state), respectively. then the temperature drops to t2= 100°c as the result of heat transfer to the surroundings. determine: a) quality of the steam at the end of the process, b) heat transfer with the surroundings. for: p1.5 mpa and t 240°c: enthalpy of superheated vapour is 2900 kj/kg, specific volume of superheated vapour is 0. 1483 m/kg, while for t 100°c: enthalpy of saturated liquid water is 419kj/kg, specific volume of saturated liquid water is 0.001043m/kg, enthalpy of saturated vapour is 2676 kj/kg, specific volume of saturated vapour is 1.672 m/kg and pressure is 0.1 mpa.

If a particle moves along a path such that r : (3 sin t) m and ? : 2t rad, where t is in seconds. what is the particle's acceleration in m/s in 4 seconds? a)- 16.43 b)- 16.29 c)- 15.21 d)- 13.79

The thermal expansion or contraction of a given metal is a function of the f a)-density b)-initial temperature c)- temperature difference d)- linear coefficient of thermal expansion e)- final temperature f)- original length