Transient processes are not [[Steady State|steady-state]], and have a finite duration. These processes are transitional in terms of system [[Mass|mass]]. For example, filling a tank with [[Fluid|fluid]]. The [[First Law of Thermodynamics|first law]] for a transient flow process is dependent on the mass that will flow in to the system, the mass that will flow out of the system​, the mass in the system at the end of the process​, and the mass that was in the system at the start of the process. $A=\sum m_e\left(h_e+\dfrac{v_e^2}{2}+gz_e\right)−\sum m_i\left(h_i+\dfrac{v_i^2}{2}+gz_i\right)$ $B=m_2\left(u_2+\dfrac{v_2^2}{2}+gz_2\right)−m_1\left(u_1+\dfrac{v_1^2}{2}+gz_1\right)$ $Q−W=A+B$ Where: - $Q$ is the net [[Heat|heat]] flowing into the system - $W$ is the net [[Work|work]] flowing out of the system - $m_e$, $m_i$, $m_2$, and $m_1$ are the [[Mass|mass]] that has flowed out of the system, the mass the flowed in, the final mass, and the initial mass respectively - $h$ is specific [[Enthalpy|enthalpy]] - $u$ is specific [[Internal Energy|internal energy]] - $v$ is [[Velocity|velocity]] - $g$ is the [[Local Gravitational Acceleration|local gravitational acceleration]] - $z$ is the [[Distance|distance]] from the ground