Heat flows from one body to other when they have, 26. Metals are good conductors of heat because, 16. Metals are good conductors of heat because (a) their atoms collide frequently (b) their atoms-are relatively far apart (c) they contain free electrons (d) they have high density (e) all of the above. Often times electrical or electronic components are housed in sealed enclosures to prevent the ingress of water, dust or other contaminants. In order to calculate the surface temperature, T 3, as a result of ID scale formation, ho is first calculated from equation 4 given the design parameters of Uo, r3, n, hs, and for the clean tube condition. Thus, the thermal conductivity of a gas increases with increase in temperature. thermal conductivity of scale, W/M-C (Btu/ hr-ft-F). Thermal conductivity of water at 20°C is of the order of (a) 0.1 (b) 0.23 (c) 0.42 (d) 0.51 (e) 0.64. Initially, when the rate of heat transfer is high, the hot water has a temperature of 70°C and the cold water has a temperature of 5°C. Save my name and email in this browser for the next time I comment. Currently, he is working in the sheet metal industry as a designer. Heat is closely related with (a) liquids (b) energy (c) temperature     (d) entropy (e) enthalpy. It is commonly denoted by $${\displaystyle k}$$, $${\displaystyle \lambda }$$, or $${\displaystyle \kappa }$$. Cork is a good insulator because it has, 19. Mechanical Subjectwise Basic Concept Notes ,Articles, Thermal Engineering Projects List - Abstract , Report, Modes of Heat Transfer- Conduction, Convection, Radiation, Heat and Mass Transfer MCQ Objective Question and Answers Part 3, Heat and Mass Transfer MCQ Objective Question and Answers Part 2, Heat Transfer Analysis of Engine Cylinder Fins Having Triangular Shape, Heat Transfer Online Notes , Objective and Interview Questions, Thermodynamics Basic Objective Type Question And Answers, Types Of Heat Exchanger | Basic Of Heat Transfer, Heat Treatment | Material Science Interview Question and Answers. There are several ways to measure thermal conductivity; each is suitable for a limited range of materials. Ans: b, 23. Ans: c, 15. Thermal conductivity of air with rise in temperature, 25. The thermal conductivity of clathrate hydrates is five times lower than that of ice near the melting point, and even lower (by a … In contrast with most well-defined crystalline structures, in which the thermal conductivity falls with increasing temperature following a T−1 dependence (for T>100 K), the thermal conductivity of clathrate hydrates increases slightly with increasing temperature (Tse and White, 1988). and Ans. Hydraulic seals - Definition, Types, Diagram , Function, Failure, Application. Ans: d. 20. (e) convert saturated steam into dry steam. 1. If What you looking for is not here, you may send a request to modify articles, Notes, and Content modification, Feedback, Suggestions here (Team will reply as early as Possible ):  Contact Form or Using Whatsapp, © 2020 Copyright Learn Mechanical Engineering, Heat and Mass Transfer MCQ Objective Question and Answers Part 1. same as lower than higher than none of these. The time constant of a thermocouple is (a) the   time   taken   to   attain   the   final temperature to be measured (b) the time taken to attain 50% of the value of initial temperature difference (c) the time taken to attain 63.2% of the value of initial temperature difference (d) determined by the time taken to reach 100°C from 0°C (e) none of the above. When heat is Transferred by molecular collision, it is referred to as heat transfer by, 11. It may be considered as a vertical shaper. For most liquids, the thermal conductivity (the rate at which energy is transferred down a temperature gradient) falls with increasing temperature but this occurs only above about 130 °C … Thermal conductivity of air with rise in temperature (a) increases (b) decreases (c) remains constant (d) may increase or decrease depending on temperature (e) none of the above. Heat transfer in liquid and gases takes place by, 12. As the hot water begins to cool and the cold water begins to warm, the difference in their temperatures decrease and the rate of heat transfer decreases. Ans: b. Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. (a) change vapour into liquid. How to calculate the temperature rise in a sealed enclosure. The thermal conductivity of a material is a measure of its ability to conduct heat. Ans: e, 17. Learn how your comment data is processed. Thermal conductivity of water in general with rise in temperature (a) increases (b) decreases (c) remains constant (d) may increase or decrease depending on temperature (e) none of the above. The two containers have a 65°C difference in temperature. This site uses Akismet to reduce spam. ⇒ Thermal conductivity of water in general with rise in temperature increases decreases remains constant may increase or decrease depending on temperature ⇒ The wet bulb temperature at 100% relative humidity is _____ dry bulb temperature. Heat flowing from one side to other depends directly on (a) face area (b) time (c) thickness (d) temperature difference (e) thermal conductivity. thermal conductivity of metal, W/M-C (Btu/ hr-ft-F). Introduction to Slotting Machine : Thermal conductivity is the property of a particular substance and shows the ease by which the process takes place. Cork is a good insulator because it has (a) free electrons (b) atoms colliding frequency (c) low density     (d) porous body (e) all of the above. Which of the following is expected to have highest thermal conductivity, Mechanical MCQ Objectives Question and Answers, Technical Mechanical Interview Question and Answers. 19. Ans: d, 22. The concept of overall coefficient of heat transfer is used in heat transfer problems of, 27. Unit of thermal conductivity in M.K.S. Thermal conductivity of water in general with rise in temperature (a) increases (b) decreases (c) remains constant (d) may increase or decrease depending on temperature (e) none of the above. Heat flowing from one side to other depends directly on, 15. In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by, 28. Solution (By Examveda Team) Apart from liquid metals, water has the highest thermal conductivity of any liquid. Thermal conductivity of water at 20°C is of the order of (a) 0.1 (b) 0.23 (c) 0.42 (d) 0.51 (e) 0.64. When heat is Transferred by molecular collision, it is referred to as heat transfer by (a) conduction       (b) convection (c) radiation (d) scattering (e) convection and radiation. Ans: a, 25. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos. Your email address will not be published. The amount of heat flow through a body by conduction is (a) directly proportional to the surface area of the body (b) directly proportional to the temperature difference on the two faces of the body (c) dependent upon the material of the body (d) inversely proportional to the thickness of the body (e) all of the above. Thank you For Visiting. Ans: d, 13. When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by, (c) increase the temperature of a liquid of vapour, (d) convert water into steam and superheat it. When the air humidity in the tunnel becomes excessively high, the thermal insulation material tends to absorb water, leading to significant changes in thermal conductivity. Since oil is a liquid it has the tendency to 'leak' through every gas/slot it finds during movement. Ans: d. 20. Ans: d, 20. Temperature of steam at around 540°C can be measured by, 22. link to Hydraulic seals - Definition, Types, Diagram , Function, Failure, Application, link to Slotter Machine - Types, Parts, Operations, Diagram, Specification.