Thermo And Fluids

Front 1

Practical reasons why the Carnot cycle is impractical as an operating cycle for a power station

Back 1

- temperature limitation
- high pump work because of steam/ water mix
- wet steam causes turbine problems
- condensation limits
- low specific work output

Front 2

Main problem with CFC refrigerants and how its changing with use of non-CFC refrigerants

Back 2

CFC (chlorofluorocarbons) refrigerants allow
more ultraviolet radiation into the earth’s
atmosphere by destroying the protective ozone
layer and thus contributing to the greenhouse
effect that causes the global warming. As a
result the use of some CFCs (e.g. R-11, R-12,
and R-115) are banned by international
treaties.
alternative - air or water refrigeration but these are not on par with modern refrigeration yet

Front 3

Reasons why ideal reverse Carnot cycle is unsuitable as a practical operating refrigeration cycle
differences between ideal reverse Carnot cycle and practical operating compression refrigeration cycle

Back 3

practically unsuitable because
- expansion turbine in stages 3-4 is expensive and impractical
- evaporation is difficult to stop at stage 1
- pumping or compressing a mix of liquid and gases as is from stage 1-2 is difficult
- there is a low specific heat transfer for a large plant size
main reasons for differences because irreversibilities in components
In practice, the refrigerant enters the compressor at state 1, slightly superheated vapor, instead of saturated vapor in the ideal cycle.
The compressor is not internally reversible in practice
Heat rejection and addition in the condenser and evaporator do not occur in constant
pressure (and temperature) as a result of pressure drop in the refrigerant.

Front 4

Why is the overall thermal efficiency of a gas turbine engine more readily affected by process irreversibility's' than a steam cycle such the Rankine.
why is gas turbine cycle more readily effect by irreversibilities than the rankine cycle

Back 4

1

Front 5

How does the Otto air standard cycle relate to the four-stroke car engine.
differences

Back 5

ideal 4 stroke cycle
1-2 isentropic compression
2-3 constant volume heat addition
3-4 isentropic expansion
4-1 constant volume heat rejection
used for internal combustion four stroke engine
only fires every other stroke

Front 6

Importance of Carnot cycle
equation for efficiency

Back 6

most efficient cycle operating between two resources
Theoretically most efficient cycle for converting a given amount of thermal energy into work, or creating a temperature difference (e.g. refrigeration) by doing a given amount of work.
no heat engine operating between a source and a sink can have a greater efficiency than an ideal reversible engine operating between the same source and sink
ideal efficiency n = W/QH = 1-(QL/QH) = 1-(TL-TH)

Front 7

Differences Carnot Cycle and Rankine with Superheat

Back 7

efficiency - carnot > RSH > reheat
dryness fraction - reheat > RSH > carnot
ssc - reheat >RSH > carnot
average temperature at which heat is absorbed is lower for the Rankine cycle.

Front 8

advantages of feed heaters in power stations

Back 8

2

Front 9

differences between heat pump and refrigeration cycle

Back 9

3

Front 10

disadvantages of gas turbine as power plant for cars
regeneration of exhaust heat to improve efficiency

Back 10

4

Front 11

Rankine cycle
Rankine cycle with super heat
Rankine cycle with reheat

Back 11

5

Front 12

Otto cycle
Diesel cycle
Mixed cycle

Back 12

6

Front 13

reversed heat engine

Back 13

7