The working substance is a phase-change
fluid. That is, it can exist as a subcooled liquid,
superheated
vapor, or as a mixture of saturated liquid and vapor. Example:
R-134a is executing a vapor-compression refrigeration cycle.
PC/PC Model
Combined cycles using two different phase-change fluids can be analyzed with this model. Two choices for selecting the working fluid model make it necessary to individually specify the working fluid for each state. Example: A vapor-compression cycle with steam is executed on top of a vapor-compression cycle with R-12 as the working fluid.
Gases:
PG Model
Obeys the ideal
gas equation
(pv=RT). Moreover, the specific heats are assumed constant. A perfect gas (PG) , thus, is a simplified ideal gas. Example:
Air is the working fluid of a reversed Brayton cycle.
IG Model
Obeys the ideal gas equation (pv=RT). Specific heats are temperature dependent; therefore, the IG model is more accurate than the PG model. Example:
Air (variable specific heats) is the working fluid of a reversed
Brayton
cycle .
n-IG Model
The working fluid can be a general mixture of ideal gases (n-IG). Form the mixture just once with up to sixty gases and use it as the working fluid for the entire cycle. Example: Reversed Brayton cycle with a working fluid that must be modeled as a mixture of gases.
PC/IG Model
Combined cycles using a phase-change (PC) fluid for one cycle and an ideal gas (IG) for another can be analyzed with this daemon. Two choices for selecting the working fluid make it necessary to individually specify the working fluid for each state. Example: A vapor-compression refrigeration cycle with R-12 is executed on top of a reversed Brayton cycle with nitrogen as the working fluid.
Vapor
Refrigeration
Cycle
Carnot
Refrigeration
Cycle
Animations of vapor and gas refrigeration cycles. For more examples of refrigeration cycles, visit VT.Chapter-10 pages.
