by Maryam Hussain How the working of a theoretical engine was proposed? The theoretical heat engine was proposed by Sadi Carnot in 1824 . Heat engines are devices that can convert heat into mechanical energy. Like a Steam engine or Motor vehicle, the working principle of all heat engines is the same in which any working substance gas or vapor is brought back to the initial stage by going through different thermodynamic stages of a cyclic process . Carnot suggested that, if a heat engine goes through fixed thermodynamic stages of a specified process, then the efficiency of the heat engine may be 100% possible. Ideally, this engine gives maximum efficiency. No other engine can be more efficient than this. The specified cyclic process suggested by Carnot is called the Carnot cycle. The Carnot engine has four main parts: 1). First, an insulated, non-conducting stand , so that the transfer of energy is not possible . 2). Second, a hot reservoir with infi...
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...