Thermal Engineering (TEN) 22337 MCQ for MSBTE mechanical engineering 3rd sem
thermal engineering mcq msbte TEN Thermal Engineering Course Code:- 22337 MCQ for mechanical engineering for MSBTE i-scheme 3rd sem.
| Subject | subject details |
|---|---|
| Program: | Diploma in Mechanical engineering |
| Program Code | ME |
| Scheme | I |
| Semester | 3 |
| Course: | Thermal Engineering |
| Course Code | 22337 |
1.A definite area or a space where some thermodynamic process takes place, is known as (a) thermodynamic cycle (b) thermodynamic process
(c) thermodynamic system (d) thermodynamic law
Answer: - Option c
Explanation: - NA
2.When neither mass nor energy is allowed to cross the boundary of a system, it is then called
(a) closed system (h) open system
(c) isolated system (d) none of these
Answer: - Option c
Explanation: -NA
3 Which of the following is the extensive properly of a thermodynamic system?
(a) pressure (h) volume
(c) temperature (d) density
Answer: - Option b
Explanation: -Depends on mass
4.Which of the following is an intensive property of a thermodynamic system?
(a) volume (b) temperature
(c) mass (d) energy
Answer: - Option b
Explanation: - Does not depend on mass
5. Which of the following is not a thermodynamic property?
(a) pressure (b) temperature
(c) heat (d) specific volume
Answer: - Option c
Explanation: -It is Path function
6.When a process or processes are performed on a system in such a way that the final state is identical with the initial state, it is then known as
(a) thermodynamic cycle (b) thermodynamic property
(c) thermodynamic process (d) zeroth law of thermodynamics
Answer: - Option a
Explanation:- NA
7.Atmospheric pressure is equal to
(a) 1.013 bar (b) 101.3 kN/m2
(c) 760 mm of Hg (d) All of these
Answer: - Option d
Explanation: - All values are equivalent
8.First law of thermodynamics deals with
(a) conservation of heat (b) conservation of momentum
(c) conservation of mass (d) conservation of energy
Answer:-Option d
Explanation:- NA
9.Second law of thermodynamics defines
(a) heat (b) work
(c) entropy (d) internal energy
Answer: - Option c
10.Kelvin-Planck's law deals with
(a) conservation of work (b) conservation of heat
(c) conservation of mass (d) conversion of heat into work
Answer: Option d
Explanation: - This statement is related with Heat Engine
11.The property of a working substance which increases or decreases as the heat is supplied or removed in a reversible manner, is known as
(a) enthalpy (b) internal energy (c) entropy (d) external energy
Answer: - Option c
Explanation: - Entropy is function of heat transfer
12.The entropy may be expressed as a function of
(a) pressure and temperature (b) temperature and volume
(c) heat and work (d) all of these
Answer: - Option a
Explanation: -NA
13.The change of entropy when heat is absorbed by the gas is
(a) positive (b) negative (c) positive or negative (d) None
Answer: - Option a
Explanation:- Entropy always increases in all real processes
14. In a steady flow process,
(a) the mass flow rate is constant (b) the heat transfer rate is constant
(c) the work transfer rate is constant (d) all of the above
Answer: - Option d
Explanation: -Characteristics of process.
15.The work done in steady flow process is given by
Answer: - Option d
Explanation: - Formula
16.The ratio of specific heat at constant pressure (Cp) and specific heat at constant volume (Cv) is
(A) equal to one (b) less than one (c) more than one (d) none of these
Answer: - Option c
Explanation: - Cp is always > Cv
17.Which of the following is not a steady flow device?
(a) Condenser (b) Turbine
(c) Tyre getting filling of air (d) Nozzle
Answer: Option c
Explanation: -Unsteady device
18.Thermodynamics does not consider
(a) initial and final state b) time factor
(c) bulk of matter d) energy change
Answer: Option b
Explanation:- It considers equilibrium states only.
19.A system which can neither exchange matter nor energy with the surroundings is called_
(a) Open system (b) Isolated system
(c) Closed system (d) Ideal system
Answer: Option b
Explanation:- Definition
20.Water at its freezing point, in a closed insulated vessel, represents a/ an
a) open system b) heterogeneous system
c) closed system d) homogeneous system
Answer: Option b
Explanation:- Mixed phases
21. The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body
(a) move actually (b) do not move actually
(c) affect the intervening medium (d) does not affect the intervening medium
Answer: -Option b
Explanation: - Basic Concept
22.The heat transfer takes place according to
(a) zeroth law of thermodynamics (b) first law of thermodynamics
(c) second law of thermodynamics (d) Stefan's law
Answer: -Option c
Explanation: - Heat transfer is defined particularly by second law.
23. The rate of heat flow through a body is Q= kA(T1 —T2)/x The term x/kA is known as
(a) thermal coefficient (b) thermal resistance
(c) thermal conductivity (d) none of these
Answer: -Option b
Explanation: - Definition
24.The thermal conductivity of sold metals .....with rise in temperature.
(a) remains same (b) decreases (c) increases
Answer: -Option b
Explanation: - It increases resistance to heat flow.
25.The overall coefficient of heat transfer is used in problems of
(a) conduction (b) convection (c) radiation
(d) conduction and convection (e) conduction and radiation.
Answer: -Option d
Explanation: - To consider effects of both.
26.The literature of heat transfer generally recognizes distinct modes of heat transfer. How many modes are there?
a) One b) Two
c) Three d) Four
Answer: c
Explanation: There are three modes of heat transfer i.e. radiation, convection and conduction.
27. Consider system A at uniform temperature t and system B at another uniform temperature
T , (t > T). Let the two systems be brought into contact and be thermally insulated from their surroundings but not from each other. Energy will flow from system A to system B because of
a) Temperature difference b) Energy difference
c) Mass difference d) Volumetric difference
Answer: a
Explanation: Greater the temperature imbalance the higher would be the rate of energy transfer.
28. Unit of the rate of heat transfer is
a) Joule b) Newton
c) Pascal d) Watt
Answer: d
Explanation: Unit of heat transfer is Joule but the rate of heat transfer is joule per second i.e. watt.
29. Convective heat transfer coefficient doesn’t depend on
a) Surface area b) Space
c) Time d) Orientation of solid surface
Answer: a
Explanation: It is denoted by h and is dependent on space, time, geometry, orientation of solid surface.
30.The rate equation used to describe the mechanism of convection is called Newton’s law of cooling. So rate of heat flow by convection doesn’t depend on
a) Convective heat transfer coefficient b) Surface area through which heat flows
c) Time d) Temperature potential difference
Answer: c
Explanation: It is directly proportional to all of above except time.
31.Thermal conductivity is maximum for which substance
a) Silver b) Ice
c) Aluminum d) Diamond
Answer: d
Explanation: Thermal conductivity of diamond is 2300 W/m K.
32.A radiator in a domestic heating system operates at a surface temperature of 60 degree Celsius.
Calculate the heat flux at the surface of the radiator if it behaves as a black body
a) 697.2 W/m2 b) 786.9 W/m2
c) 324.7 W/m2 d) 592.1 W/m2
Answer: a
Explanation: As, q = Q/A = 5.67 x 10-8 (273+60)4 = 697.2.
33.Which of the following is an example of forced convection?
a) Chilling effect of cold wind on a warm body
b) Flow of water in condenser tubes
c) Cooling of billets in the atmosphere
d) Heat exchange on cold and warm pipes
Answer: b
Explanation: In forced convection, the flow of fluid is caused by a pump, fan or by atmospheric winds
34.For a cylindrical rod with uniformly distributed heat sources, the thermal gradient at half the radius location will be
a) One half b) One fourth
c) Four times d) Twice
Answer: a
Explanation: t = t w + q g (R2 – r2)/4k. (d t /d r) r = R/2 = 1/2(d t/d r) r = R.
35.The value of transmissivity may vary from
a) 0-1 b) 1-2
c) 3-4 d) 4-5
Answer: a
Explanation: This is a very small quantity. The response of the body to incident radiations is, however, completely independent of and unaffected by the simultaneous emission from the body.
36.A condenser in a steam power plant
(a) increases expansion ratio of steam (b) reduces back pressure of steam
(c) reduces temperature of exhaust steam (d) all of these
Answer: Option d
Explanation:- It does all these functions.
37.The temperature of condensate is ......on leaving the condenser than that of circulating water at inlet.
(a)higher (b) lower
Answer: Option a
Explanation:- Actual working condition
38.A condenser where circulating water flows through tubes which are Surrounded by steam, is known as
(a)surface condenser (b) jet condenser
(c) barometric condenser (d) evaporative condenser
Answer: Option a
Explanation:- Surface heat exchange
39.The ratio of actual vacuum to the ideal vacuum in a condenser is called
(a) condenser efficiency (b) vacuum efficiency
(c) boiler efficiency (d) nozzle efficiency
Answer: Option b
Explanation:- Measure of vaccum
40.The actual vacuum in a condenser is equal to
(a) barometric pressure + actual pressure (b) barometric pressure - actual pressure
(c) gauge pressure + atmospheric pressure (d) gauge pressure - atmospheric pressure
Answer: Option b
Explanation:- Definition
41.Steam condenser converts steam into water.
a) True b) False
Answer: Option a
Explanation:- Steam condenser is a device which converts steam into water or in which steam is condensed into water. The heat rejected by the steam during condensation is absorbed by cooling water.
41.Steam condensers help in maintaining high back pressure on the exhaust side of the piston of a steam engine.
a) True b) False
Answer: Option b
Explanation:-Steam condensers maintain very low back pressure at the exhaust side of the piston of a steam engine (or a turbine). This improves the quality of expansion of steam, steam expands to a greater extent and turbine efficiency is increased.
42.Sub-atmospheric pressure is also called
a) Gauge pressure b) Absolute pressure
c) Vacuum pressure d) High altitude pressure
Answer: Option c
Explanation:- Sub-atmospheric pressure is vacuum pressure. Sub-atmospheric pressure is measured as the pressure depression below atmospheric pressure. Absolute pressure is measure taking perfect vacuum as reference.
43.Which of the following is NOT an element of a steam condensing plant?
a) Supply of cooling water b) Turbine
c) Condenser d) Wet air pump
Answer: Option b
Explanation:- A steam condensing plant consists of a condenser, supply of cooling water, hot well, wet air pump and an arrangement for recooling of cooling water (for surface condensers). Hot well is where the condensate is discharged.
44.Discharging condensate to hot well improves plant efficiency because
a) condensate is not wasted b) condensate cools down faster in the hot well
c) feed water for boiler is taken from the hot well d) it increases the pressure in the hot well
Answer: Option c
Explanation:- When the condensate is discharged into the hot well, the temperature of the water inside the hot well increases as it absorbs heat from the hot condensate. Since, the feed water temperature for the boiler is increased, the overall plant efficiency is increased.
45.Steam condensers are classified into
a) jet condensers and fast condensers b) jet condensers and surface condensers
c) high condensers and surface condensers d) slow condensers and jet condensers
Answer: Option b
Explanation:- Condensers are mainly classified into two categories – Jet condensers and surface condensers. In case of jet condensers, the cooling water comes in direct contact with the exhaust steam while in surface condensers the cooling water and exhaust steam does not come in direct contact.
46.Cooling water is sprayed into the exhaust steam in
a) steam condensers b) surface condensers
c) jet condensers d) jet condensers and high condensers
Answer: Option c
Explanation:- Usually in jet condensers, the cooling water is sprayed into the exhaust steam. This provokes rapid condensation of the steam. It can be observed that in jet condensers cooling water comes in direct contact with the exhaust steam.
47. Which of the following statements is TRUE about single-pass condenser?
a) It is a type of jet Condenser
b) The flow of water is in one direction only
c) The water flows in one direction through some tubes and returns through the remainder
d) It is not used to condense steam
Answer: Option b
Explanation:- A single-pass condenser is a type of surface condenser. In this water flows in only one direction through the tubes. The cooling water does not come in direct contact with the exhaust steam.
48.Which of the following statements is FLASE about steam condensers?
a) Jet condensers are cheaper than surface condensers
b) Cooling water comes direct contact with the exhaust steam in jet condensers
c) Cooling water does not come in direct contact with exhaust steam in surface condensers
d) Jet condensers are further classified into single-pass and double-pass condensers
Answer: Option d
Explanation:- Single-pass and Doubles-pass condensers belong to the category of surface condensers. In both type of condensers, the steam passes around tubes containing cooling water. The cooling water does not come in direct contact with the steam.
49.Which of the following statements is FALSE about double-pass condensers?
a) The water flows in one direction through some tubes and returns through the remainder
b) Exhaust steam flows through the tubes, while cooling water passes over the outer surface of the tubes
c) It is a type of surface condenser
d) Cooling water doesn’t come in contact with the exhaust steam
Answer: Option b
Explanation:- Double-pass condensers are a type of surface condensers. Cooling water flows through the tubes and exhaust steam passes over the outer surface of the tubes. The water in the tubes flows in one direction through some tubes and returns through the remainder.
50.Which of the following statements is not a correct reason for inefficiency in surface condensers?
a) Air leakage b) High resistance faced by the steam while entering
c) Condensate under cooling d) Circulating water passing through the condenser almost smoothly
Answer: Option d
Explanation:- Circulating water passes through the condenser with high friction and at a velocity not consistent with high efficiency, this results in increased inefficiency in surface condensers. Since the pressure inside the condenser is less than atmospheric, air leaks into the condenser. This limits the amount of work done by unit mass of steam, thus, results increases inefficiency.
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