Answer:
The Two reasons are :-
1. Combustion efficiency
2. Standardization of test conditions as non-luminous flame.
Explanation:
A luminous flame isn't suitable for heating as it gives out soot (A black powdery or flaky substance consisting largely of amorphous carbon, produced by the incomplete burning of organic matter)
There are following layers in earth atmosphere
a) Troposhere: the innermost layer or lowest part of atmosphere
b)stratosphere: next to troposhere
c)mesosphere:above stratosphere, here lowest temperature is observed
d)Thermosphere and Ionosphere: This layer allows long distance radio communication
e)Exosphere: this layer separates outer space from earth's surface.
Systems can exist in three ways as open systems, closed systems, and isolated systems. The main difference between open and closed system is that in an open system, matter can be exchanged with the surrounding whereas, in a closed system, matter cannot be exchanged with the surrounding.
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