Electricity for Refrigeration, Heating, and Air Conditioning
9th Edition
ISBN: 9781285179988
Author: Russell E. Smith
Publisher: Cengage Learning
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Chapter 11, Problem 3RQ
What is the major difference between a magnetic starter and a contactor?
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2 A metal block of mass m = 10 kg is sliding along a frictionless surface with an initial speed
Vo, as indicated below. The block then slides above an electromagnetic brake that applies a
force FEB to the block, opposing its motion. The magnitude of the electromagnetic force
varies quadratically with the distance moved along the brake (x):
10
FEB = kx²,
with k
= 5
N
m²
V₁ = 8 m/s
m = 10 kg
FEB
Frictionless surface
Electromagnetic brake
⇒x
Determine how far the block slides along the electromagnetic brake before stopping, in m.
Q1: Determine the length, angle of contact, and width of a 9.75 mm thick
leather belt required to transmit 15 kW from a motor running at 900 r.p.m. The
diameter of the driving pulley of the motor is 300 mm. The driven pulley runs at
300 r.p.m. and the distance between the centers of two pulleys is 3 meters. The
density of the leather is 1000 kg/m³. The maximum allowable stress in the
leather is 2.5 MPa. The coefficient of friction between the leather and pulley is
0.3. Assume open belt drive.
5. A 15 kW and 1200 r.p.m. motor drives a compressor at 300 r.p.m. through a pair of spur gears having
20° stub teeth. The centre to centre distance between the shafts is 400 mm. The motor pinion is made
of forged steel having an allowable static stress as 210 MPa, while the gear is made of cast steel
having allowable static stress as 140 MPa. Assuming that the drive operates 8 to 10 hours per day
under light shock conditions, find from the standpoint of strength,
1. Module; 2. Face width and 3. Number of teeth and pitch circle diameter of each gear.
Check the gears thus designed from the consideration of wear. The surface endurance limit may be
taken as 700 MPa. [Ans. m = 6 mm; b= 60 mm; Tp=24; T=96; Dp = 144mm; DG = 576 mm]
Chapter 11 Solutions
Electricity for Refrigeration, Heating, and Air Conditioning
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- 4. G A micarta pinion rotating at 1200 r.p.m. is to transmit 1 kW to a cast iron gear at a speed of 192 r.p.m. Assuming a starting overload of 20% and using 20° full depth involute teeth, determine the module, number of teeth on the pinion and gear and face width. Take allowable static strength for micarta as 40 MPa and for cast iron as 53 MPa. Check the pair in wear.arrow_forwardI want to solve these choicesarrow_forward2. A spur gear made of bronze drives a mid steel pinion with angular velocity ratio of 32: 1. The pressure angle is 14½. It transmits 5 kW at 1800 r.p.m. of pinion. Considering only strength, design the smallest diameter gears and find also necessary face width. The number of teeth should not be less than 15 teeth on either gear. The elastic strength of bronze may be taken as 84 MPa and of steel as 105 MPa. Lewis factor for 14½½ pressure angle may be taken 0.684 0.124 y = No. of teeth as [Ans. m 3 mm; b= 35 mm; Dp = 48 mm; D= 168 mm]arrow_forward
- Q2. Determine the safety factors for the bracket rod shown in Figure 2 based on both the distortion-energy theory and the maximum shear theory and compare them. Given: The material is 2024-T4 aluminum with a yield strength of 47 000 psi. The rod length /= 6 in. and arm a = 8 in. The rod outside diameter od 1.5 in., id = 1 in, h=2 in., t=0.5 in., Load F= 1000 lb. Assumptions: The load is static and the assembly is at room temperature. Consider shear due to transverse loading as well as other stresses. (Note: solve in SI units) wall tube Figure 2 armarrow_forwardThe question has been set up with all the cuts needed to accurately derive expressions for V(x) and M(x). Using the cuts free body diagrams set up below, derive expressions for V(x) and M(x). If you use the method of cuts then validate your answers using calculus or vice versa.arrow_forwardIt is required to treat 130 kmol/hr of chloroform-air feed gas mixture that contains 12% chloroform. It is required to remove 93% of chloroform using 150 kmol/hr of solvent that contains 99.6% water and 0.4% chloroform. The cross sectional area of the column is 0.8 m². Calculate the column height using the following data; kx'.a = 1.35 (kmol/m³.s (Ax)), and ky'.a = 0.06 (kmol/m³.s (Ay)), kx/ky = 1.35, and the equilibrium data are: X 0 0.0133 0.033 y 0 0.01 0.0266 0.049 0.064 0.0747 0.0933 0.1053 0.0433 0.06 0.0733 0.111 0.1 0.12 0.14arrow_forward
- ४ B: Find the numerical solution for the 2D equation below and calculate the temperature values for each grid point shown in Fig. 2 (show all steps). (Do only one trail using following initial values and show the final matrix) [T1] T₂ T3 [T] 1 = [0] 0 0 d dx dx) (ka)+4(ka) = dy -20xy, k = 1 + 0.3 T ge L=3cm, 4x= Ay B.Cs.: at x=0=LT=0°C at y=0-L T=10°C Fig. (2)arrow_forward: +0 العنوان use only Two rods fins) having same dimensions, one made orass (k = 85 Wm K) and the mer of copper (k = 375 W/m K), having of their ends inserted into a furna. At a section 10.5 cm a way from furnace, the temperature of brass rod 120 Find the distance at which the ame temperature would be reached in the per rod ? both ends are ex osed to the same environment. ns 2.05 ۲/۱ ostrararrow_forwardFor the beam show below, draw A.F.D, S.F.D, B.M.D 6 kN/m 1 M B. 3 M Marrow_forward
- 1. Two long rods of the same diameter-one made of brass (k=85w/m.k) and the other made of copper (k=375 w/m.k) have one of their ends inserted into a furnace (as shown in the following figure). Both rods are exposed to the same environment. At a distance of 105 mm from the furnace, the temperature of the brass rod is 120°C. At what distance from the furnace will the same temperature be reached in the copper rod? Furnace 105 mm T₁ Brass rod ⑪ h Too- x2- Ti Copper rodarrow_forward: +0 العنوان use only Two rods fins) having same dimensions, one made orass (k = 85 Wm K) and the mer of copper (k = 375 W/m K), having of their ends inserted into a furna. At a section 10.5 cm a way from furnace, the temperature of brass rod 120 Find the distance at which the ame temperature would be reached in the per rod ? both ends are ex osed to the same environment. ns 2.05 ۲/۱ ostrararrow_forwardمشر on ۲/۱ Two rods (fins) having same dimensions, one made of brass(k=85 m K) and the other of copper (k = 375 W/m K), having one of their ends inserted into a furnace. At a section 10.5 cm a way from the furnace, the temperature brass rod 120°C. Find the distance at which the same temperature would be reached in the copper rod ? both ends are exposed to the same environment. 22.05 ofthearrow_forward
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