Termo Flashcards by Deliana Collado

Common Phases of Substance

Solid, liquid & gas

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Does not take on the shape or volume of its container

Solid

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Absorb as much heat energy as it can without vaporizing

Saturated Liquid

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Example of Saturated Liquid

Liquid Water at 100C & 1 atm

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Liquid not saturated

Subcooled Liquid

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Liquid and vapor of the same substance at the same temperature and pressure

Liquid-vapor mixture
two-phase

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Ideal gas whose specific heats are constants

Perfect Gas

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Vapor that is on the verge of condensing

Saturated Vapor

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Example of Saturated Vapor

Steam at 100C & 1 atm

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Absorb more energy than is needed merely to vaparize it. It wil not condense when small amounts of energy are removed

Superheated Vapor

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Superheated vapor that behaves according to pV=mRT

Ideal Gas

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Gas that does not behave according to ideal gas laws

Real Gas

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Two or more pure gases together

Gas mixture

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atmospheric gas

Vapor-gas mixture

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Three dimensional surface that predicts a substance phase includes the following properties

Pressure
Temperature
Specific Volume
pvT diagram

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Unique state at which solid, liquid and gaseouses phases can coexist

Triple point

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(T/F) Thermodynamic properties of ideal gases do not depend on other thermodynamic properties

True. Changes in pressure do not affect changes in specific enthalpy when T constant. Changes un specific volume do not affect change in specific internal energy when T constant.

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A process which no heat crosses the system boundary

Adiabatic process
Including isentropic and throttling process.

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An adiabatic process which there is no entropy production. Is reversibec

Isentropic Process

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An adiabatic process in which there is no change in enthalpy, but for which there a significant pressure drop

Throttling process

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Isobaric Process

Constant Pressure Process

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Isothermal Process

Constant Temperature Process

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Isochoric Process

Constant volume process

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A process that obeys the polytropic equation of state.

Polytropic process

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Law: The net energy crossing the system boundary is the change in energy inside the system. Whether or not a process is reversible. The work done in adiabatic process depends only on the systems endpoint conditions.

First Law of Thermodynimics

If no mass crosses the system boundaries, the system is

closed

If mass flows through the system across the system boundaries, the system is

open

Example of Open Systems

Pumps, heat exchangers, jet engines, turbines, boilers

Example of Closed System

Gas compressed by a piston

System closed to both mass and energy, is an ____ system

isolated

Qin, Qout, Win, Wout signs

Qin - heat entrando al sistema (+) Qout - Heat saliendo del sistema (-) Win - alrededores haciendo trabajo sobre el system (-) Wout - system haciendo trabajo hacia los alrededores (+)

Closed System - P constante

wb=p*deltaV

Closed System - V constante

wb=0

Closed system - T constante

wb = RTln(v2/v1) = RTln(p2/p1)

Reversive work (Wrev) - Open systems

At the boundary, there is a pressure opposing fluid from entering the system. So the work required to cause the flow into the system against the Pexit is w_rev. It is work being done to the system (-)

Substance Phase Determine Rules - Que es? - T Psat @ T dada

Subcooled liquid 2. Liquid Vapor Ragion - T = Tsat @ P dada - P = Psat @ T dada 3. Superheated Vapor - T> Tsat @ P dada - P < Psat @ T dada

Substance Phase Determine Rules - Que es? - T = Tsat @ P dada - P = Psat @ T dada

Liquid Vapor Region - T = Tsat @ P dada - P = Psat @ T dada

Substance Phase Determine Rules - Que es? - T> Tsat @ P dada - P < Psat @ T dada

Superheated Vapor

T-s diagram Rankine System

Boiler - P aumenta - T no cambia (no delta h) Condenser (T no cambia P disminuye, no delta h) Pump - T aumenta ( no delta s *idealmente*) Turbnine - T disminuye ( no delta s *idealmente*)

Law: Environment: Entropia del ambiente siempre va a aumentar en un proceso real Working fluid: Una sustancia puede ser devuelta a su estado original sin aumentar la entropia del sistema, solo en un sistema reversible Equipment: A machine taht returns the working fluid to its original state require a heat sink. A machine that rejets more energy than the useful work it performs

2nd Law of Thermodynamics

Cycle that takes heat and uses it to do work on the surroundings

Power Cycle

Most efficient power cycle possible

Carnot Cycle

Similar to Carnot Cycle except the compression process occurs in the liquid region

Rankine Cycle

Four stroke cycle (Power Cycle)

Otto Cycle

Dry-bulb Temperature (Tdb)

Temperature that a regular thermometer measure if exposed to air

Wet-bulb Temperature Twb

Temperature of air that has gone through an adiabatic saturation process. It is measured with a thermometer that is covered with a water saturated cotton wick.

Dew-point Temperature (Tdp)

This is the dry bulb temperature at which water starts to condense when moist air is cooled in a constant pressure process. Tdp = Tsat for the partial pressure vapor

Tdb = Twb = Tdp

Saturated air

Tdp< Twb < Tdb

Unsaturated air

dQ=Tds

Proceso Reversible

(T/F) 2nd Law of thermodynamics: It is impossible for a system working in a complete cycle to accomplish, as it sole effect, the transfer of ehat from a body at a given temperature to a body at a higher temperature

True - Calsius statement of 2nd Law of thermodynamics

What are the processes in an ideal Otto Combustion cycle?

Two constant volume processes and two constant isentropic processes

In which process is the maximum work output obtained?

In a reversible process. The difference between the maximum and the actual work output is the process irreversibility.

Dalton Law of Partial Pressure

The total pressure of gas mixture is teh sum od the individual gases partial pressure.

Energy that is given off when the fuel is burned

Heating Value

Heating Value Units

Coal - KJ/kg Oil - KJ/L Gases - KJ/m3

Heat Value Derived from enthalpy of formation is known as

Enthalpy of reaction / Heat of Reaction / Heat of combustion - deltaHr

Exothermic Reaction

Chemical reactions that give off energy (negative enthalpy)

Endothermic Reaction

Absorb energy (positive enthalpy)

Hess Law

Enthalpy of reaction = sum of the enthalpies of formation of the products - sume of enthalpies of formation of the reactants.

Molar weight of air

28.84 g/mol

Volume of 1 mole of ideal gas at standard temperature and pressure is

22.4 L

The complete combustion of hydrocarbon fuel are

carbon dioxided and water vapor

When sulfure is present in the fuel, the normal product is

sulfur dioxide SO2

When there is insufficient oxygen for complete combustion, ___ wil be formed

Carbon Monoxide (CO)

Cuando se habla de una combustion de air es

O2 + 3.76N2