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# Thermals Exam 1

### RPI Thermals and Fluids Exam 1 Vocab

Question | Answer |
---|---|

Thermodynamics | The science of the conversions between forms of energy and their relations to the macroscopic measurable quantities |

Heat Transfer | Transmission of thermal energy from a hotter object to a cooler object via conduction, convection, or radiation |

Control Volume | Arbitrary volume where mass and energy flow through |

System | A flexible, fixed or moving boundary that encloses the same particles at all times |

Closed System | Also called controlled mass system (no mass can cross boundary) |

Open System | Also called Control Volume (mass and energy can cross boundary) |

Isolated System | no mass or energy can cross boundary |

First Law of Thermodynamics | energy cannot be created or destroyed only transformed |

Specific Heat | The energy required to raise the temperature of a unit mass of substance by one degree |

Ideal Solids and Liquids | Does not change volume with temperature, cannot be compressed |

Dimension | Physical Quality |

Units | Magnitudes assigned to dimensions |

Extensive Properties | The value of an overall system is the sum of its values for the parts into which the system is divided |

Intensive Properties | Non additive properties |

Property | Macroscopic characteristic of a system to which a numerical value can be assigned without the knowledge of the history of the system |

Fluid Mechanics | The study of fluids at rest or in motion and the interactions between a solid and a fluid either flowing past or acting on the solid in some manner |

Boundary or Control Surface | Drawn around the system for the identification |

Surroundings | Everything outside the boundary |

Process | occurs when some property changes or energy flows |

Unsteady/ Transient | Properties of interest are different at start and finish |

Steady | Property does not vary with time only location |

Schematic diagram | Shows relationship and interactions |

Assumption | Used to simplify a problem |

Conduction | Caused by molecular vibrations |

Convection | Moving fluid flows past a solid of a different temp |

Radiation | Occurs in a vacuum, transfer via electromagnetic waves |

Multimode | Multiple types of heat transfer used in one system |

Thermal Resistance | Resistance to heat transfer |

Hydro statics | Fluids at rest |

Fluid Dynamics | Relative motion between fluid and solid |

Fluid | A substance that will deform is a shear force is applied |

Temperature | Measure of the average kinetic energy of the molecules |

Polytropic Process | Relationship between pressure and volume |

Isobaric Process | Constant Pressure |

Isothermal Process | Constant Temperature |

Adiabatic Process | No Heat Transfer |

Continuum Assumption | Characterize the material as if it were infinitely divisible and not composed of discrete molecules |

Pressure | The force of the combined motion of many molecules |

Heat | Energy in motion across the boundary of a system |

Internal Energy | Energy is stored in a system |

Equilibrium | A state in which there are no imbalances in forces, temps, pressures, phases or chemical composition |

Quasi Equilibrium | one that passes through states of equilibrium (very slow process) |

Biot Number | The ratio of conductive resistance to convective resistance |

Fourier's Law of Conduction | Heat flows from hot to cold based on thermal Conductivity |

Black Surface | Ideal Surface for radiation - one that absorbs all the radiation incident upon it |

Gray Surface | If a fraction of the incident radiation reflected by the surface is independent of the wavelength of the incident radiation |

Diffuse Surface | if the fraction of the incident radiation does not depend on the angle of incident |

Resistance analogy | Heat transfer rate is proportional to the temperature difference |

Lumped System Approximation | If two thermal resistances are being used and one is much larger than the other |

Fourier Number | Ratio of the rate at which heat is conducted through a body to the rate at which it is stored |