Bundle: Electricity For Refrigeration, Heating, And Air Conditioning, 10th + Refrigeration And Air Conditioning Technology, 8th + Mindtap Hvac, 4 ... Whitman/johnson's Refrigeration And Air Condi
8th Edition
ISBN: 9780357261385
Author: Russell E. Smith
Publisher: Cengage Learning
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Textbook Question
Chapter 26, Problem 20RQ
How is defrost accomplished when the equipment room is in the back and the medium-temperature fixtures are in the front?
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3.
9.
10.
The centrifugal tension in belts
(a) increases power transmitted
(b) decreases power transmitted
(c) have no effect on the power transmitted
(d) increases power transmitted upto a certain speed and then decreases
When the belt is stationary, it is subjected to some tension, known as initial tension. The value of this
tension is equal to the
(a) tension in the tight side of the belt
(b) tension in the slack side of the belt
(c) sum of the tensions in the tight side and slack side of the belt
(d) average tension of the tight side and slack side of the belt
The relation between the pitch of the chain (p) and pitch circle diameter of the sprocket (d) is given by
60°
(a) p=d sin
(c) p=d sin
(120°
T
where T Number of teeth on the sprocket.
90°
(b) p=d sin
T
180°
(d) p=d sin
T
OBJECTIVE TYPE QUESTIONS
1.
The maximum fluctuation of energy is the
2.
(a) sum of maximum and minimum energies
(b) difference between the maximum and minimum energies
(c) ratio of the maximum energy and minimum energy
(d) ratio of the mean resisting torque to the work done per cycle
In a turning moment diagram, the variations of energy above and below the mean resisting torque line
is called
(a) fluctuation of energy
(b) maximum fluctuation of energy
(c) coefficient of fluctuation of energy
(d) none of the above
Chapter 16: Turning Moment Diagrams and Flywheel 611
The ratio of the maximum fluctuation of speed to the mean speed is called
3.
(a) fluctuation of speed
(c) coefficient of fluctuation of speed
4.
(b) maximum fluctuation of speed
(a) none of these
The ratio of the maximum fluctuation of energy to the.......... is called coefficient of fluctuation of
energy.
(a) minimum fluctuation of energy
(b) work done per cycle
The maximum fluctuation of energy in a flywheel is equal to
5.…
OBJECTIVE TYPE QUESTIONS
1.
The velocity ratio of two pulleys connected by an open belt or crossed belt is
2.
(a) directly proportional to their diameters
(b) inversely proportional to their diameters
(c) directly proportional to the square of their diameters
(d) inversely proportional to the square of their diameters
Two pulleys of diameters d, and d, and at distance x apart are connected by means of an open belt
drive. The length of the belt is
(a)(d+d₁)+2x+
(d₁+d₂)²
4x
(b)(d₁-d₂)+2x+
(d₁-d₂)²
4x
(c)(d₁+d₂)+ +2x+
(d₁-d₂)²
4x
(d)(d-d₂)+2x+
(d₁ +d₂)²
4x
3.
In a cone pulley, if the sum of radii of the pulleys on the driving and driven shafts is constant, then
(a) open belt drive is recommended
(b) cross belt drive is recommended
(c) both open belt drive and cross belt drive are recommended
(d) the drive is recommended depending upon the torque transmitted
Due to slip of the belt, the velocity ratio of the belt drive
4.
(a) decreases
5.
(b) increases
(c) does not change
When two pulleys…
Chapter 26 Solutions
Bundle: Electricity For Refrigeration, Heating, And Air Conditioning, 10th + Refrigeration And Air Conditioning Technology, 8th + Mindtap Hvac, 4 ... Whitman/johnson's Refrigeration And Air Condi
Ch. 26 - The two broad categories of display cases are...Ch. 26 - How are conditions maintained in open display...Ch. 26 - What are mullion heaters?Ch. 26 - The three temperature ranges for refrigeration...Ch. 26 - The two methods for rejecting heat from...Ch. 26 - When the compressors are located in the equipment...Ch. 26 - When one large compressor is used, what desirable...Ch. 26 - Define a parallel compressor system and list five...Ch. 26 - Three disadvantages of parallel compressor systems...Ch. 26 - What is the difference between an even and an...
Ch. 26 - Exactly matching the refrigeration load with the...Ch. 26 - What is the function of the pressure transducer in...Ch. 26 - What is the function of the microprocessor-based...Ch. 26 - Explain how the oil separator, oil reservoir,...Ch. 26 - Large or small compressors on parallel compressor...Ch. 26 - A(n)_______varies the frequency of an...Ch. 26 - Prob. 17RQCh. 26 - Prob. 18RQCh. 26 - Three advantages of unitary, stand-alone...Ch. 26 - How is defrost accomplished when the equipment...Ch. 26 - True or False: The two types of defrosts used with...Ch. 26 - What special precautions should be taken with...Ch. 26 - Prob. 23RQCh. 26 - What special valve is used in a refrigerated air...Ch. 26 - Briefly explain what is meant by a surge-type...Ch. 26 - Briefly explain what is meant by a subcritical...Ch. 26 - Briefly explain what is meant by a transcritical...Ch. 26 - Prob. 28RQCh. 26 - Prob. 29RQCh. 26 - Prob. 30RQCh. 26 - Prob. 31RQCh. 26 - Prob. 32RQCh. 26 - Prob. 33RQ
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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 Warrow_forward9. 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.arrow_forward7. 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 approxiarrow_forward
- 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
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