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Thursday, 30 June 2016

SIGN CONVENTION FOR HEAT AND WORK TRANSFER IN THERMODYNAMICS

We have seen the basic concepts and also method of calculations of heat energy transfer and work energy transfer in the field of thermal engineering. Where we have discussed work energy transfer and heat energy transfer separately in thermodynamics.

As we have already pointed out that during calculation of heat energy transfer and work energy transfer, we must understand the sign conventions used for heat and work energy transfer in thermodynamics.

Let us see here the sign conventions used for heat energy and work energy transfer

Following figure displayed here indicates the sign conventions for heat and work energy interactions in thermodynamics.

Sign convention for heat energy transfer

If heat energy is added to the system from surrounding, quantity of heat energy transferred will be considered as positive. If heat energy is rejected from the system to the surrounding, quantity of heat energy transferred will be considered as negative.

Sign convention for work energy transfer

If work is done by the system over its surrounding, quantity of work energy transferred will be considered as positive. If work is done over the system from its surrounding, quantity of work energy transferred will be considered as positive.

We will see another topic i.e.
Displacement work or PdV work in thermodynamicsin thermodynamics in our next post.
Do you have suggestions? Please write in comment box.

Reference:

Engineering thermodynamics by P. K. nag
Engineering thermodynamics by r. k. Rajput
Image courtesy: Google

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