P M V Subbarao Professor Mechanical Engineering Department Thermodynamics of EMM P M V Subbarao Professor Mechanical Engineering Department First Level of Models for Energy Efficiency…

Science always has its origin in the adaptation of thought to some definite field of experience. 400 BC Sir Ernst Mach 800 BC

Haystock Boiler, 1725

James Watt’s Engine :The Artificial Horse Evolved over 100 Years James Watt radically improved Newcomen's engine (1769) by condensing the steam outside the cylinder .

Steam Engine : First decade of 19th Century

Questions Raised by Nicholas Leonard Sadi Carnot How was the work developed by the engine related to the heat supplied (amount of coal burned)? Was there an upper limit to this work and what condition could lead to its release? Was water the best material to use, or might not some other liquid such as alcohol provide a more effective medium? Might not a gas such as air be more advantageous than a condensable vapour? The thermal efficiency of boiler has increased from about 30% in 1800 to over 90% in a modern boiler….

Energy is a manageable expense — perhaps our most manageable expense! Definition of EMM The judicious and effective use of energy to maximize profits (that is, minimize costs) and enhance competitive positions. - Capehart, Turner and Kennedy –1997 Implementation of EMM demands a strong belief: Energy is a manageable expense — perhaps our most manageable expense!

Energy is a Manageable Expense!!! What are your top three operating expenses? Answer: For many organisations, they are energy (electricity, coal and oil/gas), labour and materials expenses. 2. Through careful management, by what percentage could you reduce each expense? Answer. Many companies have realised as much as 25% savings in energy costs by implementing an energy management program. What priority should energy management receive? Answer: In terms of the potential for savings, many companies find that energy moves to the first priority position. In fact, energy management would deliver about twice the savings that materials management would and five times what labour cost management offers.

A EMM Model Of A Manufacturing System Creation of Energy Sources for Manufacturing System Manufacturing System Material Processing System Creation of Energy Sources for Material Processing System

Energy considerations at different manufacturing levels

Process Efficiency of A Manufacturing Device A device following a Reversible process will produce maximum benefits for a specified amount of resource depletion. Irreversible or actual devices generate relatively lower magnitude of benefits. The level of this process irreversibility is also defined as efficiency of a process or machine. Conventional thermodynamics uses various performance parameters. For example, a machine is expected to follow an Isentropic process. However, due to friction it may be following an irreversible adiabatic or irreversible and heat loss process. This irreversibility is defined as Isentropic Efficiency.

Isentropic Efficiency of a Device Isentropic efficiency is defined for a process. This is the ratio of actual performance to Isentropic performance of a machine. For power generation machines: Isentropic efficiency = Actual power output/Isentropic power output. For Power consuming machines: Isentropic efficiency = Isentropic power input/Actual Power input. These definitions are case dependent and a separate definition is to be developed for each application.

Types of Work Transfers in Manufacturing Moving Boundary work (displacement work) Extrusion Metal cutting Forging Shaft work Electrical work Steam/gas work

Displacement work : Extrusion Extrusion is the process by which a block/billet of metal is reduced in cross section by forcing it to flow through a die orifice under high pressure. Most metals are hot extruded due to large amount of forces required in extrusion.

Direct Extrusion of Hallow Parts

Theoretical Minimum Energy for Heating Metal The theoretical minimum energy requirements to melt one ton of metal. This is defined as the difference in the theoretical total energy content (enthalpy) of metal at typical tapping temperatures and the total energy at ambient temperatures. The enthalpy of metal is considered zero at 25°C. The energy levels for a metal at other temperatures is calculated using:

C 25 182 427 538 760 954 1232 1510 1650

Enthalpy vs. Temperature

Thermodynamic Process for Extrusion

Simple Processes for Displacement Work