- #1
Roboto
- 13
- 1
Here is a fun question for you heat transfer experts.
I have a high pressure waterjet firing into a open tank of water. The hydraulic power of the jet entering the tank is known, along with the flow rate of the jet entering into the tank. All of the energy of the jet is dissipated into the large volume of water in the tank. The volumetric flow rate of water leaving the tank is equal to the volumetric flow rate of the water entering the tank. Tank volume of water remains constant.
Typically the heating input is the mass flow rate of the water times its specific heat and temperature is the input. But with a high pressure waterjets, there is the very high kinetic energy aspect to the incoming water.
On the one hand one can just assume the all of the hydraulic power is converted into heat and that is the sole input. But we are also adding water to the tank that is mixing with the water in the tank and a then leaving the tank of water. So then, does one add to the input to the tank the mass flow rate of the water and its specific heat and incoming temperature with the heat of the hydraulic power? Or does one use the water heating component of the jet, and then using the difference between the water fraction and the total hydraulic power entering the tank as additional energy to be added to the tank with the water component.
The puzzling point is that the input is a single water input that has a single mass flow rate, but also has an extremely high kinetic energy. How one handles this yields very different heating rates of the tank of water. I am trying to avoid double counting something or miss accounting for something.
Intuition says to use the hydraulic power plus the heating from the water's mass flow rate and temperature. but I keep wrestling with myself thinking that I am double counting energy sources.
I have a high pressure waterjet firing into a open tank of water. The hydraulic power of the jet entering the tank is known, along with the flow rate of the jet entering into the tank. All of the energy of the jet is dissipated into the large volume of water in the tank. The volumetric flow rate of water leaving the tank is equal to the volumetric flow rate of the water entering the tank. Tank volume of water remains constant.
Typically the heating input is the mass flow rate of the water times its specific heat and temperature is the input. But with a high pressure waterjets, there is the very high kinetic energy aspect to the incoming water.
On the one hand one can just assume the all of the hydraulic power is converted into heat and that is the sole input. But we are also adding water to the tank that is mixing with the water in the tank and a then leaving the tank of water. So then, does one add to the input to the tank the mass flow rate of the water and its specific heat and incoming temperature with the heat of the hydraulic power? Or does one use the water heating component of the jet, and then using the difference between the water fraction and the total hydraulic power entering the tank as additional energy to be added to the tank with the water component.
The puzzling point is that the input is a single water input that has a single mass flow rate, but also has an extremely high kinetic energy. How one handles this yields very different heating rates of the tank of water. I am trying to avoid double counting something or miss accounting for something.
Intuition says to use the hydraulic power plus the heating from the water's mass flow rate and temperature. but I keep wrestling with myself thinking that I am double counting energy sources.