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by   Maryam Hussain What is natural gas? Natural gas is a mixture of gaseous hydrocarbons. Natural gas is composed mainly of methane, ethane, propane, and butane which all are highly flammable. Natural gas is primarily employed as a clean heating fuel in industry, commercial installations, and households. Inflammability and toxicity of natural gas? When natural gas comes out of the ground at its source, it has neither color nor smell . Companies that supply gas to consumers add the very noticeable odor of rotten eggs to gas so that a leak is easy to detect because of its odor only. If you should ever smell a strong odor of natural gas, do not use any devices that might make a spark. Light switches, phones, and even turning on a flashlight could ignite the gas and cause an explosion. Leave your home immediately and take anyone else in the house with you, including pets. Natural gas is lighter than air, non-toxic , and contains no poisonous ingredients. Breathing ...

  by  Maryam Hussain Why do refrigerators’ compressor runs for longer durations & waste electrical energy? Required compartment temperatures: The ideal temperature inside (the lower section of) a refrigerator is between 36˚ and 38˚ F. For a freezer, the temperature should range between –5˚ and 5˚ F. If you think that your refrigerator and freezer are too warm or too cold, test them by putting a thermometer in the refrigerator and freezer cabinets for a couple of hours each, and check the readings. If they’re high or low w.r.t above mentioned ranges, adjust the temperature controls up or down to reach the correct temperature. If the temperature controls don’t fix the problem, further troubleshooting is required. Leaky gaskets of a refrigerator door: The doors of the refrigerator and freezer of your unit are fitted with rubber gaskets to seal the cold air inside. If the gasket is worn out, the compressor has to work with overtime to keep up, which increases...

by  Maryam Hussain How much salary should you demand? While you are undergoing a job interview, the employer may bring up the salary and benefits issues earlier, but you should avoid asking benefits-related questions until you are offered the job. The right time of discussing salary and benefits comes after you have been offered. Of course, if the employer raises these issues, you may ask questions in response to what the employer has raised, but even then avoid letting this area become the all-consuming focus of discussion prior to the job offer. Once the job has been offered to you, you should start asking benefits-related questions; if the topic of salary and benefits has not been discussed earlier,  you should start the topic by asking about the salary range for the position. Try to talk in terms of a range rather than a single salary figure. Discussing a range will give greater flexibility for some negotiations. Usually, there is room for some negotiation i...

by   Maryam Hussain What is a catalyst? A catalyst is a material that increases the rate and selectivity of a chemical reaction. Whenever a catalytic reaction occurs, cyclic regeneration of the catalyst is required to maintain the catalytic activity. On the basis of the physical phases of reactants and the catalysts, there are two types of catalytic reactions and here only one of those will be described. The type of catalytic reaction in an automobile’s catalytic converter is called heterogeneous catalysis . How do the catalytic reactions occur? In this process, reactants (CO, O 2 , NOx, HC, etc.) adsorb onto the surface of a solid catalyst and are activated by chemical interaction with the catalyst surface, and are then rapidly and selectively transformed to adsorbed products, which desorb from the catalyst surface and go away to the environment through the exhaust pipe. Once the product is desorbed from the surface of the catalyst, the catalyst returns to its orig...

by Maryam Hussain When to operate a controller on MANUAL and AUTOMATIC control modes? To illustrate the need to operate a controller on MANUAL and AUTOMATIC control modes for controlling a process, let us consider an example of a shell and tube heat exchanger in which a process stream, on the tube side, is heated by condensing steam on the shell side. The objective of this heater is to supply the process fluid, at a specific temperature, to the downstream process otherwise the whole production will be upset . If this supply temperature deviates due to some reasons (there may be several causes/disturbing variables), then some action must be taken to correct the deviation. One way to achieve this objective is through the “monitor and control” job performed by the process plant operator. The operator observes the supply temperature of process stream Ta, compares it with the desired temperature Ts, and, on the basis of this comparison, decides whether to throttle or un-ch...

by  Maryam Hussain Is temperature depending on the mass or size of a body? Temperature   is a macroscopic characteristic of any system such to which a numerical value can be assigned at a given time without knowledge of the previous behavior, history, of the system. Hence the temperature is an intensive property of a system because its value is independent of the size or extent of a system and may vary from place to place within the system at any moment. If we wish to measure the temperature of an elephant under his left ear and then under his right ear, then it will be same for both of a 500 kg elephant or for a 700 kg elephant. Therefore, the temperature of the whole body is not the sum of the temperatures of the parts of that body . Temperature is a technical term that is quantifies the amount of internal energy possessed by a substance. How to define the temperature? Temperature is defined as the degree of “hotness” or “coldness” of a body. We use our sense o...