Electricity for Refrigeration, Heating, and Air Conditioning
9th Edition
ISBN: 9781285179988
Author: Russell E. Smith
Publisher: Cengage Learning
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Textbook Question
Chapter 1, Problem 12RQ
True or False: The correct fuse size for an electrical circuit is one that is sized twice as large as needed for circuit protection.
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Q3:
(10 MARKS)
A piston with a weight of 29.4 N is supported by a spring
and dashpot. A dashpot of damping coefficient c = 275
N.s/m acts in parallel with the spring of stiffness k = 2400
N/m. A fluctuating pressure p = 960 sin 30t N/m² acts on
the piston, whose top surface area is 0.05 m². Determine
the steady-state displacement as a function of time and the
maximum force transmitted to the base.
P=Po sin cot
W
9. Design a spur gear drive required to transmit 45 kW at a pinion speed of 800 r.p.m. The velocity ratio
is 3.5 : 1. The teeth are 20° full-depth involute with 18 teeth on the pinion. Both the pinion and gear
are made of steel with a maximum safe static stress of 180 MPa. Assume a safe stress of 40 MPa for
the material of the shaft and key.
10. Design a pair of spur gears with stub teeth to transmit 55 kW from a 175 mm pinion running at 2500
r.p.m. to a gear running at 1500 r.p.m. Both the gears are made of steel having B.H.N. 260. Approximate
the pitch by means of Lewis equation and then adjust the dimensions to keep within the limits set by
the dynamic load and wear equation.
7. A motor shaft rotating at 1440 r.p.m. has to transmit 15 kW to a low speed shaft rotating at 500 r.p.m.
The teeth are 20° involute with 25 teeth on the pinion. Both the pinion and gear are made of cast iron
with a maximum safe stress of 56 MPa. A safe stress of 35 MPa may be taken for the shaft on which
the gear is mounted. Design and sketch the spur gear drive to suit the above conditions. The starting
torque may be assumed as 1,25 times the running torque.
Ruins 20 LW at 100 nm to another shaft running approxi
Chapter 1 Solutions
Electricity for Refrigeration, Heating, and Air Conditioning
Ch. 1 - True or False: A heating and air-conditioning...Ch. 1 - What is a live electrical circuit?Ch. 1 - Which of the following voltages will a...Ch. 1 - Electrical shock occurs when a person _________....Ch. 1 - What are the important elements of electrical...Ch. 1 - Prob. 6RQCh. 1 - Which of the following is the standard by which...Ch. 1 - Prob. 8RQCh. 1 - What type of ladder should the technician use on...Ch. 1 - What precautions should be taken when you see a...
Ch. 1 - True or False: It is recommended that at least one...Ch. 1 - True or False: The correct fuse size for an...Ch. 1 - What is the difference between a two-prong plug...Ch. 1 - Which prong on a three-prong plug is the ground?...Ch. 1 - True or False: A grounding adapter does no good if...Ch. 1 - An electrical device that will open an electrical...Ch. 1 - True or False: Receptacles used on the job site...Ch. 1 - What precautions should you use when working in an...Ch. 1 - What is the difference between a fuse and a...Ch. 1 - List at least five electrical safety rules that...
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- 6. A two stage reduction drive is to be designed to transmit 2 kW; the input speed being 960 r.p.m. and overall reduction ratio being 9. The drive consists of straight tooth spur gears only, the shafts being spaced 200 mm apart, the input and output shafts being co-axial.arrow_forward2 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.arrow_forwardQ1: 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.arrow_forward
- 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]arrow_forward4. 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_forward
- 2. 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_forwardQ2. 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_forward
- It 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_forward४ 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_forward
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