♨Along with all the above assumptions, taking constant specific heats at room temperature, at 25 C for air, is called cold air standard assumptions. ✔
Assuming constant specific heats at room temperature 25 C for air
is only the difference between air standard assumptions and cold-air standard assumptions.
What are standard air assumptions?
The following assumptions are commonly known as the air- standard assumptions: 1- The working fluid is air, which continuously circulates in a closed loop (cycle).
Air is considered as ideal gas
. … 4- The exhaust process is modeled by a heat-rejection process that restores the working fluid (air) at its initial state.
What are the assumptions of an air standard analysis cold air standard analysis?
These assumptions are: (1)The working fluid is air, which continuously circulates in a closed loop and always behaves as an ideal gas. (2)
All the processes are internally reversible.
(3)The combustion process is replaced by a heat addition process. (4)The exhaust process is replaced by a heat rejection process.
What is cold air standard analysis?
Cold-Air-Standard Assumption –
Used to simplify the analysis of gas cycles
. Includes all of the air-standard assumptions in addition to the assumption that the working fluid (air) has constant specific heats.
Which is the wrong assumptions for calculation of air standard efficiency?
All processes are reversible.
Specific heat remains constant at all temperatures
. No account of the mechanism of heat transfer is considered. Gases dissociate at higher temperatures.
What are the air standard assumptions in thermodynamic heat engines?
The Air-Standard Assumptions. Heat is
tranferred to the working fluid at constant pressure from the external heat source
, usually the exhaust gases from a combustion reaction.
Why is air standard analysis used?
This results in a series of cycles in which the energy is received and rejected at variable temperature. These cycles can be used to
examine the performance of internal combustion engines
, e.g. petrol and diesel engines and gas turbines.
What are the assumptions in fuel air cycles?
The working fluid is assumed to be a perfect gas
. There is no change in the mass of the working medium. All the process that constitutes the cycle is reversible. Heat is assumed to be supplied from a constant high-temperature source and not from chemical reaction during the cycle.
Which of the following is NOT assumption of air standard cycle?
Which one of the following is NOT a necessary assumption for the air-standard Otto cycle? All processes are both internally as well as externally reversible. Intake and
exhaust processes are constant volume heat rejection processes
. The combustion process is a constant volume heat addition process.
Which cycle is more efficient?
Explanation:
Otto cycle
is more efficient than Diesel cycle for a given compression ratio. 6. For constant maximum pressure and heat input, the air standard efficiency of the gas power cycle is in the order.
What is an air standard efficiency?
Air standard efficiency is taken as
the ideal efficiency of an internal combustion engine
. … This would mean that whatever the temperature of the charge reached during combustion, the final temperature would have to be absolute zero.
What is meant by air standard cycle?
Air standard cycle is defined as
a reversible heat engine in which the source of heat supply and the sink for heat rejection are external to the air
. This cycle is a good approximation for many so-called internal combustion cycles.
Is a assumption made in Carnot cycle?
Assumptions of Carnot Cycle
While proposing the processes, Carnot made certain assumptions as given below:
There is no friction at all between the piston and cylinder and other moving parts of the engine
, thus there is no heat generated and lost due to friction.
What are the methods to increase the efficiency of Rankine cycle and explain any one?
Increasing the operating pressure of the boiler, automatically raises the temperature at which boiling takes place
. This raises the average temperature at which heat is added to the steam and thus raises the thermal efficiency of the cycle..
What are the assumptions for an ideal gas?
For a gas to be “ideal” there are four governing assumptions: The gas particles have negligible volume. The gas particles are equally sized and do not have intermolecular forces (attraction or repulsion) with other gas particles.
The gas particles move randomly in agreement with Newton’s Laws of Motion.
What is the thermal efficiency of diesel engine?
A typical diesel automotive engine operates at
around 30% to 35%
of thermal efficiency. About 65-70% is rejected as waste heat without being converted into useful work, i.e. work delivered to wheels. In general, engines using the Diesel cycle are usually more efficient, than engines using the Otto cycle.
