Question

Why is it important to define specific mission scenarios (or operational profiles) within the context of the system operational requirements?

Answer 1

Defining specific mission scenerio is important because it may change the entire design concept. Some products likes pumps, compressor, turbine, heat exchangers etc are always rated under particular system. For example, An Air conditioner is rated as 2TR at suppose say 35°C ambient for maintaining 23°C indoor conditions. The rated energy consumption at same temperatures is say 2KW. Now, same Air conditioner is taken into desert condition whether ambient is 45°C, indoor condition again 23°C (Note : cooling load is 2TR only maybe smaller room! ). In such conditions, same unit will be giving only 1.6 to 1.8TR of cooling and will consume minimum of 2.4KW energy. Why so? Because, the components of air conditioning system ie compressor work is increased at the heat removed in first case was from 24°C to 35°C ie against temperature difference of 11°C while in second case, temperature difference was 21°C. The refrigerant returning from evaporator would be at higher temperature, thus compression will take place at higher temperature. Similarly, all systems like pump, compressor, turbines, gear, shaft etc etc any object we can think of is designed to work under certain conditions.

Hence, before designing any product, it is very important to define specific mission scenerio or sometimes the operational profile so that the designer has understanding of conditions at which product has to operate. It helps define the product quality, safety, maintainence, lifecycle and also predict its failure.

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