空调专业毕业设计外文翻译.docxVIP

附录B 英文翻译THERMODYNAMICS AND REFRIGERATION CYCLESTHERMODYNAMICS is the study of energy, its transformations, and its relation to states of matter. This chapter covers the application of thermodynamics to refrigeration cycles. The first part reviews the first and second laws of thermodynamics and presents methods for calculating thermodynamic properties. The second and third parts address compression and absorption refrigeration cycles, two common methods of thermal energy transfer.THERMODYNAMICSA thermodynamic system is a region in space or a quantity of matter bounded by a closed surface. The surroundings include everything external to the system, and the system is separated fromthe surroundings by the system boundaries. These boundaries can be movable or fixed, real or imaginary. Entropy and energy are important in any thermodynamic system. Entropy measures the molecular disorder of a system. The more mixed a system, the greater its entropy; an orderly or unmixed configuration is one of low entropy. Energy has the capacity for producing an effect and can be categorized into either stored or transient forms.Stored EnergyThermal (internal) energy is caused by the motion of molecules and/or intermolecular forces.Potential energy (PE) is caused by attractive forces existing between molecules, or the elevation of the system. (1)wherem =massg = local acceleration of gravityz = elevation above horizontal reference planeKinetic energy (KE) is the energy caused by the velocity of molecules and is expressed as(2)where V is the velocity of a fluid stream crossing the system boundary.Chemical energy is caused by the arrangement of atoms composing the molecules.Nuclear (atomic) energy derives from the cohesive forces holding protons and neutrons together as the atom’s nucleus.Energy in TransitionHeat Q is the mechanism that transfers energy across the boundaries of systems with differing temperatures, always toward the lower temperature. Heat is positive when energy is added to