Refrigerant-134a enters an adiabatic compressor as saturated vapor at 160 kPa at a rate of 2.8 m3/min and is compressed to a pressure of 900 kPa. Determine the minimum power that must be supplied to the compressor. Use the tables for R-134a.
The minimum power that must be supplied to the compressor
In: Mechanical Engineering
CHOCHITO, S.A homemade sweets factory wants to determine the normal time and standard time for packaging and packaging of its variety of products. The following table contains the data about a recent study, regarding the measurement of the elements to be carried out. A measurement is considered incorrect if it has a variability greater than +/- 10%, therefore it must be eliminated from the calculation. Knowing that the company grants its workers 30 minutes for the necessary delay and fatigue:
Work elements Cycles in minutes R
| 1. Take a container | 1.7 | 1.8 | 2.2 | 1.7 | 2.3 | 1.9 | 2.1 | 1.8 | 2.2 | 1.7 | 130% |
| 2. Fill the container | 4.3 | 5.7 | 4.4 | 5.6 | 4.6 | 5.5 | 4.6 | 5.4 | 4.7 | 5.3 | 120% |
| 3. Cover the container | 3.4 | 4.6 | 3.5 | 4.5 | 3.6 | 4.4 | 3.7 | 4.3 | 3.8 | 4.2 | 110% |
| 4. Place the label | 1.9 | 2.1 | 1.8 | 2.2 | 1.7 | 2.3 | 1.8 | 2.2 | 1.7 | 2.3 | 120% |
| 5. Place 24 containers per box | 2.3 | 1.8 | 2.2 | 1.7 | 2.3 | 1.9 | 2.1 | 1.8 | 2.2 | 1.7 | 140% |
|
6. Stack the full boxes |
7 | 9 | 6.8 |
9.2 |
6.9 | 9.1 | 7.1 | 8.9 | 7.2 | 8.8 | 120% |
Calculate:
a. Normal time and standard time
b. Calculate the number of boxes per worker
In: Mechanical Engineering
How Engineering Economy helps engineers for optimized decision?
In: Mechanical Engineering
Can there be multiple optimal solutions to an assignment problem? How to identify such situations
In: Mechanical Engineering
What do you understand by break down maintenance? Discuss the various features of breakdown maintenance management?
In: Mechanical Engineering
Do maintenance management principles have any relevance in the service industry?
In: Mechanical Engineering
Explain the following briefly :
Redundancy
Availability
Maintainability
In: Mechanical Engineering
In: Mechanical Engineering
Air enters the compressor of a regenerative air-standard Brayton
cycle with a volumetric flow rate of 60 m3/s at 0.8 bar,
280 K. The compressor pressure ratio is 20, and the maximum cycle
temperature is 1950 K. For the compressor, the isentropic
efficiency is 92% and for the turbine the isentropic efficiency is
95%.
For a regenerator effectiveness of 86%, determine:
(a) the net power developed, in MW.
(b) the rate of heat addition in the combustor, in MW.
(c) the percent thermal efficiency of the cycle.
In: Mechanical Engineering
Problem 8.045 SI
Consider a regenerative vapor power cycle with two feedwater
heaters, a closed one and an open one, and reheat. Steam enters the
first turbine stage at 12 MPa, 560°C, and expands to 2 MPa. Some
steam is extracted at 2 MPa and fed to the closed feedwater heater.
The remainder is reheated at 2 MPa to 520°C and then expands
through the second-stage turbine to 0.3 MPa, where an additional
amount is extracted and fed into the open feedwater heater
operating at 0.3 MPa.
The steam expanding through the third-stage turbine exits at the
condenser pressure of 60 kPa. Feedwater leaves the closed heater at
210°C, 12 MPa, and condensate exiting as saturated liquid at 2 MPa
is trapped into the open feedwater heater. Saturated liquid at 0.3
MPa leaves the open feedwater heater. Assume all pumps and turbine
stages operate isentropically.
Determine for the cycle:
(a) the heat transfer to the working fluid passing through the
steam generator, in kJ per kg of steam entering the firststage
turbine.
(b) the percent thermal efficiency.
(c) the heat transfer from the working fluid passing through the
condenser to the cooling water, in kJ per kg of steam entering the
first-stage turbine.
In: Mechanical Engineering
In: Mechanical Engineering
The 4 lb particle is subjected to the action of its weight and
forces
F1={2i+6j−2tk}lb,
F2={t2i−4tj−1k}lb,
and F3={−2ti}lb, where
t is in seconds. Determine the distance the ball is from
the origin 5 s after being released from rest.
(Figure 1).
In: Mechanical Engineering
A tank contains 21 kg of dry air and 0.3 kg of water vapor at 30°C and 100 kPa total pressure. Determine
(a) The specific humidity
(b) The relative humidity
(c) The specific enthalpy of the mixture in the tank as (kJ/kg-mixture) (calculate by hand)
(d) The specific enthalpy of the mixture in the tank as (kJ/kg-dry air) (calculate by hand)
(e) Explain (in 1-2 sentences) the difference between the values in c and d – which value agrees with the enthalpy value in the psychrometric chart at this condition?
In: Mechanical Engineering
A circular loop which possesses 55 turns is placed in a uniform magnetic field. The direction of the magnetic field makes an angle of 70 o with respect to the normal direction to the loop. The magnetic field strength B is increased at a constant rate from B1 =3T to B2 =17T in a time interval of 20 s. If Ф1 is 3.99 Wb,
a) What is the radius of the wire? (PLEASE THOROUGHLY EXPLAIN)
b) What is the EMF?
c) What is the current if the electrical resistance of the loop is 7 ohms?
In: Mechanical Engineering
In: Mechanical Engineering