Engineering Answers

A bakery oven is constructed of refractory material having an

average thermal conductivity of 0.8 Btu/hr-ft-F. The inside dimension

of the oven are 7’ x 6’ x 2’. If the wall of the oven is 4.5 in. thick and

the temperature of the inner and outer surfaces are 1200F and 200 F,

respectively, what is the total heat loss per day in the oven wall?

A hollow sphere with 4 in. inside diameter and 12 in. outside 

diameter has an inner surface temperature of 500 F and outer 

surface temperature if 300 F. If the thermal conductivity of the 

sphere material is 25 Btu/hr-ft-F, what is the rate of heat flow?

A hollow sphere of pure iron contains a liquid chemical

mixture which releases 1,000,000 Btu/hr. If the inside diameter

and the outside of the sphere is 0.5 ft. and 1 ft., respectively,

determine the inner surface temperature of the sphere assuming

the outside surface temperature is 100 F.

A 6-in. nominal diameter mild steel pipe (OD=6.625 in.) has an inside

surface temperature of 500 F. The pipe is covered with a 3 in. layer

of 85 percent magnesia insulation which has a surface temperature

of 100 F. Determine the heat loss in Btu/hr-100 ft of pipe.

k for magnesia = 0.043Btu/hr-ft-F

k for steel = 28.2

Estimate the heat transfer loss on a chimney having 12 cm inside

diameter insulated by 6 cm refractory cement. The inside and outside

temperature are 200 C and 30, respectively. If the chimney is 20 ft.

long, what is the total heat loss by conduction on the wall. Assume

k=0.138 kcal/hr-m-C.

The wall of the rice hull furnace is made up of 9 in. of fire

brick (k=0.72 Btu/hr-ft℉), 5in.of insulating brick (k=0.08

Btu/hr-ft-F)and 7.5 in. of red brick (k=0.5 Btu/hr-ft-F) . The

inner and outer surface temperatures 𝑡1 and 𝑡4 are 1500℉

and 150℉, respectively. Neglecting the resistances of the

mortar joints, compute the temperatures 𝑡2 and 𝑡3 at the

contact surface.

A rice hull furnace is to be designed to consume rice hull

at a rate of 5 sack/hour (10 kg/sack). If the furnace has an

outside dimension of 1 m wide x 1.5 m long x 1.2 m high,

what is the percentage heat loss by conduction from the

wall of the furnace? The wall is insulated by 8 in. thick brick

material. Inside and outside temperature are 400℃ and

40℃ , respectively.

Estimate the heat transfer rate on a rice hull furnace wall 

1 m x 1 m 1x 1m outside dimension. The inside temperature 

of the furnace is 800℃ while the outside is 28 ℃. the furnace 

insulation is 0.19 m thick red brick with heat conductibility of 

0.74 Kcal/hr-m- ℃. also compute the percentage heat loss 

of the furnace assuming it consumes rice hull ay a rate of 15 

kg/hr (3000 Kcal/kg). Neglect heat losses at the corner and 

edges of the furnace. Tfurnace wall = 800 ℃

The angular acceleration 𝛼, rad/s2 of a rotating disk is related to its angular velocity 𝜔, rad/s by 𝛼 = 4 √𝜔. When t = 0, the disk is at rest and the angular position coordinate of a line in the disk is θ = 8rad. Find the expression for θ(𝜔).

7, The lengths of crank and connecting rod of a horizontal

reciprocating engine are 100 mm and 500 mm respectively. The

crank is rotating at 400 rpm. When the crank has turned 300 from

inner dead center, find analytically, (i) the velocity and

acceleration

of the slider, (ii) the angular velocity, and angular acceleration of

theconnecting rod.