In a counter-flow heat exchanger,
a. both hot and cold fluid will enter at one side and leave at the other side
b. parallel to each other enter from opposite sides to each other
c. enter at perpendicular directions to each other
d. all of the above

Afour cylinder four-stroke in-line engine has a stroke of 160mm, connecting rod length of 150mm, a reciprocating mass of 3kg and its firing order is 1-3-4-2. the spacing between cylinders is 100mm. i. show that the engine is in balance with regard to the primary inertia forces and primary 3. a and secondary inertia couples. li determine the out of balance secondary inertia force ii. propose ways of balancing this out of balance force and discuss the challenges that will arise