Question

Consider an infinitesimally small fluid element moving along with the flow. Apply the first law of thermodynamics to this model. Which of these statements is correct?

(a) The rate of change of the total energy is equal to the rate of heat addition and work extraction

(b) The rate of work extraction is equal to the rate of heat addition and the rate of change of the total energy

(c) The rate of heat addition is equal to the rate of work extraction and the rate of change of the total energy

(d) The rate of change of the total energy is equal to the rate of work extraction

The question was posed to me by my college director while I was bunking the class.

My enquiry is from Energy Equation in portion Governing Equations of Fluid Dynamics of Computational Fluid Dynamics

Answer 1

Correct choice is (a) The rate of change of the total energy is equal to the rate of heat addition and work extraction

To explain I would say: The first law of thermodynamics applied to a system states that “The rate of change of the total energy is equal to the rate of heat addition and work extraction”.