BUET ENGINEERS

  MECHANICAL ENGINEERING ONE LINER  1. What is the difference between scavenging and supercharging ? Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air. 2. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes. Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively. 3. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ? It will decrease. 4. Why entropy change for a reversible adiabatic process is zero ? Because there is no heat transfer in this process. 5. What are two essential conditions of perfect gas ? It

MECHANICAL ENGINEERING ONE LINER 1. What is the difference between isotropic and anisotropic materials? If a material exhibits same mechanical properties regardless of loading direction, it is isotropic, e.g., homogeneous cast materials. Materials lacking this property are anisotropic. 2. What are orthotropic materials?  It is a special class of anisotropic materials which can be described by giving their properties in three perpendicular directions e.g. wood; composites. 3. What is view factor?  View factor is dependent upon geometry of the two surfaces exchanging radiation. 4. What properties need to be considered for applications calling for following requirements:  (i) Rigidity (ii) Strength for no plastic deformation under static load. (iii) Strength to withstand overload without fracture. (iv) Wear resistance  (v) Reliability and Safety.  (i) Rigidity—Elastic modulus and yield strength  (ii) Strength (for no