Author: workhouse123
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HOOKE’S LAW
Hooke’s law states that stress and strain are proportional to each other under elastic limit. Originally, Hooke’s law specified that stress was proportional to strain but later Thomas Young introduced constant of proportionality which is known as Young’s modulus of elastic. Further, this name was superseded by modulus of elasticity. Figure 12.3 demonstrates the Hooke’s Law. Figure…
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INTRODUCTION TO STRESS AND STRAIN
There are certain behaviours of all materials under the influence of external force. Stress and strain are one of the measures to show these behaviours. Stress is a resistive force per unit area, which is developed internally to oppose the external force subjected to the material. Strain is a measure of deformation of the material…
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PSYCHROMETRY
Psychrometry is the study of air–water vapour mixtures. It is also sometimes referred to as hygrometry. Many mechanical engineering devices exploit psychrometric processes, such as air conditioning systems and cooling towers. Two important principles upon which psychrometric relationships are based are the perfect gas equation and Dalton’s law regarding the mixture. The perfect gas equation, PV = RT,…
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TYPES OF REFRIGERATORS
A refrigerator maintains the temperature slightly higher than the freezing point of the water. There is a freezer which maintains the temperature below the freezing point of water. As far as the classification of refrigerators is concerned, it can be widely classified into four classes. They are top-mount freezer refrigerator, side-by-side refrigerators, freezer on bottom,…
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Vapour Compression Refrigeration System
roadly, the refrigeration systems can be categorized as 8.4.1 Air-refrigeration System Reversed Carnot cycle Reversed Carnot cycle is shown in Figure 8.2. It consists of the following processes. Figure 8.2 P−V and T−S Diagrams for Reversed Carnot Cycle Process a–b: Absorption of heat by the working fluid from refrigerator at constant low temperature TL during isothermal expansion. Process b–c: Isentropic compression of the working fluid with…
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COMPONENTS OF REFRIGERATION SYSTEM
The five basic components of a refrigeration system are as follows: 8.3.1 Evaporator The purpose of the evaporator is to remove unwanted heat from the product via the liquid refrigerant. The liquid refrigerant contained within the evaporator is boiling at a low pressure. The level of this pressure is determined by two factors: 8.3.2 Compressor The purpose…
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REFRIGERATOR AND HEAT PUMP
Clausius statement of the Second Law of Thermodynamics: It is impossible to construct a device that, operating in a cycle, has no effect other than the transfer of heat from a cooler to a hotter body. Thus, the Clausius statement tells us that heat will not flow from cold to hot regions without assistance of outside…
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INTRODUCTION
Initially, the main purpose of refrigeration was to conserve foods. The Chinese were the first to find out that ice increased the life and improved the taste of drinks and for centuries Eskimos have conserved food by freezing it. At the beginning of the 19th century, it had been observed that the growth of microorganisms…
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GEAR DRIVE
All the important gear terminologies are shown in Figure 15.14. Pitch Point: The point of contact between pitch circles of two gears is known as pitch point. Pitch Circle: The circle passing through point of contacts of two gears is known as pitch circle. Pitch Diameter, D: Diameter of pitch circle is known as pitch diameter. Circular Pitch, Pc: It…
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CHAIN DRIVE
To overcome the problem of slip in belt drive or rope drive, chain drive is used. A schematic diagram of chain drive is shown in Figure 15.8. The velocity ratio in chain drive remains constant. But, chain drive is heavier than the belt drive and there is gradual stretching in its strength. Time to time some of…