ChE 123: LE 2

Question 1

the IUPAC name of the refrigerant R-22 which contains one chlorine atom, is

Answer 1

chlorodifluoromethane

Question 2

the main difference between a heat pump and a refrigerator is that a heat pump delivers heat to a low0temperature reservoir, while a refrigerator removes heat from a low-temperature reservoir

Answer 2

false
the heat pump delivers heat to a high temperature reservoir which is the same with a refrigerator

Question 3

an ideal engine with V_C = 5 L, V__D = 2L; V_A = 2.5 L; V_B = 5 L operates on what cycle

Answer 3

diesel cycle

Question 4

undesirable characteristic of a refrigerant

Answer 4

high freezing point

Question 5

true or false: the efficiency of an engine based on the otto cycle is higher compared to that of an engine based on the diesel cycle at the same compression ratio

Answer 5

true

Question 6

true or false: for a refrigerator, the pressure inside the evaporator is kept high to allow low-temperature vaporization

Answer 6

false
The pressure inside the evaporator is kept low, not high. A low pressure in the evaporator allows the refrigerant to vaporize at low temperatures, which is necessary to absorb heat from the refrigerated space.

Question 7

true or false: in a carnot cycle-based steam power plant, the condenser outputs a saturated liquid-saturated vapor mixture, which requires easier pumping with less power

Answer 7

false
The condenser output is typically a saturated liquid, not a saturated liquid-vapor mixture

Question 8

true or false: superheating the steam in a Rankine Cycle before turbine expansion improves efficiency but may lead to excessive moisture at the turbine exit

Answer 8

false
The ideal Rankine cycle is typically defined with the turbine inlet steam at saturated vapor condition, not superheated.

Question 9

an ideal engine undergoes a cycle where the system occupies 3L, 2L, 2.5L, and 4L at different stages. based on these volume changes, the engine likely operates on the ______________ cycle

Answer 9

Brayton

Question 10

the temperature of most gases _____________ after expansion, both in Claude and Linde liquefaction processes

Question 11

the following methods can’t be done to liquefy gases

Answer 11

throttling of low T, low P gase

Question 12

a refrigerant that contains two carbon atoms, two fluorine toms, two chlorine atoms, two hydrogen atoms, and no bromine

Answer 12

R-132

Question 13

the refrigerant that is usually used in absorption refrigeration is _________________

Answer 13

ammonia

Question 14

the ideal rankine cycle operates on

Answer 14

two isentropic steps, two isobaric steps

Question 15

the ______________ stroke starts when the piston moves downward, reducing the cylinder pressure and allowing the air-fuel mixture (or air Diesel engines) to be drawn into the combustion chamber through the open valve

Answer 15

intake

Question 16

true or false: a higher cutoff ratio means high work output but lower thermal efficiency

Answer 16

true

Question 17

the main difference of vapor-compression cycle with the absorption refrigeration is the ____________________

Answer 17

method of compression

Question 18

true or false: throttling at appropriate conditions is one of the methods to liquefy gases

Answer 18

true

Question 19

true or false: the main difference between an otto engine and a diesel engine is that an otto engine requires electrical spark to start combustion at constant pressure while the diesel engine automatically ignites due to high temperature and high-pressure compression of the air-fuel mixture

Answer 19

false
An Otto engine (gasoline engine) uses spark ignition to start combustion. The combustion occurs approximately at constant volume, not constant pressure.

Question 20

true or false: in an ideal Rankine Cycle, superheating the working fluid before expansion through the turbine increases the thermal efficiency by raising the average temperature of heat addition, and ensures that the fluid remains in the vapor phase throughout the isentropic expansion

Question 21

an idea engine follows thermodynamic cycle where that working fluid undergoes pressure changes of 5, 30, 35, and 10 atm at key states. Based on these pressure conditions at each point in the cycle, the engine most likely operates on the?

Answer 21

otto cycle

Question 22

a refrigerant which is an isomer “b” contains two carbon atoms, two fluorine atoms, two chlorine atoms, two hydrogen atoms, and two bromine atoms. the refrigerant’s name is?

Answer 22

R-132B2b

Question 23

true or false: the Claude liquefaction process differs from a Linde liquefaction process because a turbine is used in Claude liquefaction, while a compressor is used in Linde liquefaction

Answer 23

false
The Claude process differs from the Linde process because a turbine is used in Claude for expansion, while Linde uses a throttling valve