열실험

열실험

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본문 Lift is commonly associated with the wing of a fixed-wing aircraft, although lift is also generated by propellers; kites; helicopter rotors; rudders, sails and keels on sailboats; hydrofoils; wings on auto racing cars; wind turbines and other streamlined objects. While the common meaning of the word lift assumes that lift opposes gravity, lift in its technical sense can be in any direction since it is defined with respect to the direction of flow rather than to the direction of gravity. When an aircraft is flying straight and level (cruise) most of the lift opposes gravity. However, when an aircraft is climbing, descending, or banking in a turn, for example, the lift is tilted with respect to the vertical. Lift may also be entirely downwards in some aerobatic manoeuvres, or on the wing on a racing car. In this last case, the term downforce is often used. Lift may also be horizontal, for instance on a sail on a sailboat. An airfoil is a streamlined shape that is capable of generating significantly more lift than drag. Non-streamlined objects such as bluff bodies and plates (not parallel to the flow) may also generate lift when moving relative to the fluid. 1.2 Examples of lift force Sailboat: When the boat sails into the wind , the bow is pointed into the apparent wind, which is the vector resolution of the true wind and the boat course. The sail in the wind acts as an airfoil and the hull in the water acts as a hydrofoil, so there are two sets of forces acting on a sailboat Racing car wing and spoiler: Instead of installing wing in a normal way, wing and spoiler on a racing car are both install upside-down. The wind that goes through the wing will push down the car on the road. Hydrofoil boat: At low speeds the hull (body of ship) sits in the water and the hydrofoils are totally submerged in the water. As the boat's speed increases, the hydrofoils create lift. At a certain speed, the lift produced by the hydrofoils equals thesum ofof the boat and cargo weights. Therefore the hull comes out of the water. Instead of having an increaseindrag with increasing speedbecause the hull is lifted out of the water(contrary to what happens in traditional boats due to pressure drag), the hydrofoils provide a more efficient way of cruising. Decreasing the drag contributes to the better use of the power needed for the movement of the boat. 1.3 Drag force In fluid dynamics, drag (sometimes called air resistance or fluid resistance) refers to forces which act on a solid object in the direction of the relative fluid flow velocity. Unlike other resistive forces such as dry friction, which is nearly independent of velocity, drag forces depend on velocity. Drag forces always decrease fluid velocity relative to the solid object in the fluids path. 1.4 Examples of drag Examples of drag include the component of the net aerodynamic or hydrodynamic force acting opposite to the direction of the movement of the solid object relative to the Earth as for cars, aircraft and boat hulls; or acting in the same geographical direction of motion as the solid, as for a sails on a downwind sail boat, or in intermediate directions on a sail depending on points of sail. In the case of viscous drag of fluid in a pipe, drag force on the immobile pipe decreases fluid velocity relative to the pipe. 참고문헌 10. References (1) 노승탁, "공업열역학", 1993, 문운당 (2) 서정윤, "공업열역학", 1989, 성안당 (3) E. C. Guyer, "Handbook of applied thermal design", 1989, McGraw-Hill. (4) W. F. Stoecker and J. W. Jones. "Refrigeration & Air-conditioning", 1989, McGraw-Hill. (5) 노상순 외 1명(공저), "신고 공기조화", 1991, 동명사 (6) G. S. Van Wylen & R. e. Sonntag(원저), 최인규 외 2명(공역), "공업열역학 , 1992, 보성문화사 (7) 오후규, "완성냉동공학", 1992, 한미 (8) Mcquiston, F. C., Parker, J., and Spitler, J., "Heating, Ventilating, and Air conditioning 5th edition", 2000, Wiley http://www.agf.gov.bc.ca/resmgmt/publist/200Series/280600-1.pdf http://www.alephzero.co.uk/ref/circeff.htm http://encyclopedia2.thefreedictionary.com/Refrigeration+Cycle ko.wikipedia.org http://www.ehow.com/info_8645591_kinds-refrigerants.html 히트펌프를 이용한 냉동실험 Quiz (손으로 작성) 1. 이상적인 냉동 사이클의 P-v 및 P-h선도를 그리고, 각 과정이 무슨 과정인지를 간단하게 쓰시오. 2. 이상 냉동 cycle에서 응축온도 52℃, 증발온도 -7℃이면 성적계수(COP)는 얼마인가? (숫자는 변경될 수 있음) 베타(COP) = 273-7/52+7 카르노 사이클 냉동기를 가정하여 성능계수는 다음과 같다. 3. 다음은 어떤 냉동시스템에서의 냉매의 상태값이다. 항목별로 답하시오.(풀이과정 필수) 상태 압력(MPa) 온도(℃) 엔탈피(kJ/kg) 압축기 입구 0.35 10 405 압축기 출구 1.15 60 438 증발기 입구 0.35 5 256 단, 증발기 입구와 압축기 입구의 압력강하는 없고, 질량 유동률은 일정하다. 1) 압축기의 압축일량을 구하시오.(kW) 2) 증발기의 냉동능력을 구하시오.(kW) 3) 위 시스템의 성적계수(COP)를 구하시오. 4. 일반적으로 요구되는 냉매 요구 조건(냉매의 특성)을 3가지 이상 쓰시오 하고 싶은 말 좀 더 업그레이드하여 자료를 보완하여, 과제물을 꼼꼼하게 정성을 들어 작성했습니다. 위 자료 요약정리 잘되어 있으니 잘 참고하시어 학업에 나날이 발전이 있기를 기원합니다 ^^ 구입자 분의 앞날에 항상 무궁한 발전과 행복과 행운이 깃들기를 홧팅 키워드 열실험