China
Africa
Explore chapters and articles related to this topic
First Law Analysis of Control Volumes
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
Usually, when a fluid passes through a control volume, its thermodynamic properties, intensive or extensive properties, vary along the space co-ordinates and with time. If the flow rates of mass and energy change with the time through the control surface, then mass and energy change with the time in the control volume also. Steady flow refers to the condition in which the rates of flow of mass and energy through the control surface are constant, that is, the total mass or energy entering the control volume must equal the total mass or energy leaving. The fluid properties within a control volume may vary along the space co-ordinates but remain unchanged with the time. In most of the engineering devices such as turbines, nozzles, and compressors, the flow occurs constantly under the same operating conditions for long periods of time once the flow is stabilized, i.e., the unsteady state is completed. They are classified as steady-flow devices. The steady-flow process can be suitably applied to such devices to represent the flow process. It is a process in which the fluid properties will not vary with time within the control volume, i.e., they remain constant at the inlet and exit. Moreover, heat and work interactions within the system and its surroundings also remain the same and will not vary with time. The devices such as turbines, compressors, and nozzles operate under steady-flow conditions and they are called steady-flow devices.
Introduction
Published in Greg F. Naterer, Advanced Heat Transfer, 2018
The conservation of energy, or first law of thermodynamics, is a fundamental basis of heat transfer engineering. Two general types of energy balances may be used—either a control mass or a control volume approach. A control mass refers to a closed system of no inflow or outflow of mass from the system. In contrast, a control volume refers to an open system consisting of a fixed region in space with inflows and/or outflows of mass across the boundary surfaces. A general energy balance for a control volume can be expressed as (see Figure 1.1): E˙cv=E˙in−E˙out+E˙g
Thermodynamics and Power Cycles
Published in Kenneth D. Kok, Nuclear Engineering Handbook, 2016
Thermodynamic analysis applies energy, mass, entropy, and exergy balance equations to thermodynamic systems, which are simply the matter analyzed within a defined boundary. A closed system (or control mass) is a fixed collection of matter, while an open system (or control volume) allows a fluid to cross the system boundary at various inlets or outlets (see Figure 23.2). A steam turbine, for example, is an open thermodynamic system since the working fluid crosses the system boundary at the inlet and outlet. This chapter develops the thermodynamic balance equations and provides the background material required to use them in analysis of nuclear power plants. In developing generalized balance equations the sign convention shown in Figure 23.2 is used, in which work out is positive and heat in is negative. However, a more physically based sign convention is also used where appropriate, such as defining positive pump work as work supplied to a pump. The chosen sign convention is not universal; balance equations are frequently written based on work input as positive (Eastop and McConkey, 1993).
Thermodynamic-dynamic analysis of gamma type free-piston stirling engine charged with hydrogen gas as working fluid
Published in International Journal of Green Energy, 2020
The paper presents the modeling and design of a gamma type FPSE prototype that is currently being developed. Theoretical modeling is accomplished by discretizing the working space into a network of finite one-dimensional control volumes. In the thermodynamic and dynamic parts of the study, the nodal analysis approach and Newton’s second law are applied, respectively. The conservation of mass, momentum, and energy is applied to each control volume. A computer program is written in Fortran and the governing equations are solved numerically using a fully-explicit finite difference method. Although a number of numerical studies on the FPSE have been examined, none have considering that the working gas specific heat transfer coefficient changes with temperature. In this study the all simulations were performed by regarding specific heat transfer coefficient varying with temperature.
Muddling between science and engineering: an epistemic strategy for developing human factors and ergonomics as a hybrid discipline
Published in Theoretical Issues in Ergonomics Science, 2018
In terms of having a practical effect on the practice of engineering, the science-engineering epistemological tension has undergone detailed scrutiny by both historians and philosophers of technology and engineering (e.g. Vincenti 1990; Polanyi 1964; Pitt 2001; Radder 2009, Mitcham 1994; Bunge 1966; Hong 1999 among others). In one particular case of the study of control volume analysis, the engineer-historian Walter Vincenti (1990) notes the development of engineering knowledge as differentiated from scientific knowledge. The method of control volume analysis is significantly used in fluid mechanics problems by engineers. While this aspect has been developed by engineers for their own analysis of engineering-based problems, it is not typically found in physics textbooks, even though the technique is recognised globally. For example, earlier it was incorporated in a textbook meant for engineers and physicists but subsequently dropped from a later edition of the book that was targeted only for physicists. This example is not isolated; Vincenti's book is replete with examples of flush riveting, air-propeller tests and inclusion of the pilot as a part of the aircraft (discussed as a case study in this article) to demonstrate how engineering knowledge requires a detailed understanding separate from scientific knowledge.
Design and analysis of a scooping engine valve
Published in International Journal of Ambient Energy, 2021
G. Boopathy, N. Ramanan, E. Gopi
governs the conservation of mass, which means that the rate of change of mass in an arbitrary control volume must be equal to the total mass flow over the control volume boundaries.