Newer Post Older Post Home. Subscribe to: Post Comments Atom. The best semi-trailer manufacturer Anster Special Vehicles. Search The Topic Here. Powered by Blogger. Popular Posts. We will discuss here the difference between positive and non-positive displacement pump with the help of this post. Pumps are basically We were discussing various basic concepts of thermodynamics such as thermal energy reservoir in thermodynamics in our recent post.
We hav We have discussed in our previous post about the basic of helical gears, where we have seen the various characteristics of helical gears, We were discussing the concept of laminar and turbulent flow , Reynolds experiment , frictional loss in pipes , derivation of expressio No heat energy is gained or lost by the fluids;. As the fluid passes through a pump, enthalpy of the fluid increases, internal energy of the fluid remains constant due to the increase in pv flow energy.
Increase in potential energy of fluid is the most important change found in almost all pump applications. Nozzles are devices which increase the velocity of a fluid at the expense of pressure. In nozzles fluids flow at a speed which is high enough to neglect heat lost or gained as it crosses the entire length of the nozzle. Therefore, flow through nozzles can be regarded as adiabatic. There is no shaft or any other form of work transfer to the fluid or from the fluid; that is.
Diffusers are reverse of nozzles devices which increase the pressure of a fluid stream by reducing its kinetic energy. Similar to nozzles, the following assumptions hold good for diffusers.
Heat lost or gained as it crosses the entire length of the nozzle. Heat Exchangers. Devices in which heat is transferred from a hot fluid stream to a cold fluid stream are known as heat exchangers. A throttling process occurs when a fluid flowing in a line suddenly encounters a restriction in the flow passage. It may be.
First Law for a Cyclic Process. In a cyclic process the system is taken through a series of processes and finally returned to its original state. The end state of a cyclic process is identical with the state of the system at the beginning of the cycle.
This is possible if the energy level at the beginning and end of the cyclic process are also the same. In other words, the net energy change in a cyclic process is zero. Figure 3. Hence for a cyclic process algebraic sum of heat tranfers is equal to the algebraic sum of work transfer. This was first proved by Joule, based on the experiments he conducted between and , that were the first quantitative analysis of thermodynamic systems.
Energy is a property of a system. Consider a system undergoing a process from state1 to state2 along path A as shown in Figure 3.
Let the system be taken back to the initial state 1 along two possible paths B and C. The Mach number, M, is the ratio of the flow speed, c, to the speed of sound, a. You will learn more about these quantities in fluids, but it is interesting to see that M 2 measures the ratio of the kinetic energy of the gas to its thermal energy. Homework 10 PDF. The stagnation temperature and stagnation pressure are the conditions the fluid would reach if it were brought to zero speed relative to some reference frame , via a steady, adiabatic process with no external work add quasi-static for stagnation pressure.
What if the body or reference frame is moving? We know from looking at re-entry vehicles, that the skin temperature is much hotter than the atmospheric temperature. If the atmosphere is assumed still, and we stagnate a fluid particle on the nose of a high speed vehicle carrying it along with the vehicle and thus essentially giving it kinetic energy its stagnation temperature is given by. The temperature the skin reaches to first approximation is the stagnation temperature.
The atmospheric temperature, T, is not frame dependent. The confusion comes about because T is usually referred to as the static temperature and in common language this has a similar meaning as "stagnation". In fluid mechanics and thermodynamics static is commonly used to label the thermodynamic properties of the gas p, T, etc.
Stagnation quantities are those the flow would arrive at if brought to zero speed relative to some reference frame, via a steady, adiabatic process with no external work add quasi-static for stagnation pressure. Stagnation quantities depend on the frame of reference. In turn, this will result in the following mass balance.
On the other hand, if there was one inlet but two outlets than the following mass balance equation would result. As with mass, the energy that enters a control volume during a steady flow process must be equal to the energy that leaves. This will result in the following energy balance equation. Due to the fact that energy can be transferred by heat, work, and mass, equation 4 can be expanded to the following equation.
The energy balance given in these equations is intuitive when the direction and magnitude of heat and work is known.
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