A temperature-entropy (T-S) diagram plots refrigerant properties with absolute temperature on the vertical axis and specific entropy on the horizontal axis. T-S diagrams provide clear visualization of refrigeration cycle efficiency by showing entropy generation and irreversibilities in system processes.
Technical Details
The saturation curves on T-S diagrams form a distinctive bell shape with the critical point at the apex. Constant pressure lines appear as nearly vertical curves in the two-phase region. Isentropic (constant entropy) processes appear as vertical lines, making ideal compressor and turbine processes easy to identify. The area enclosed by a cycle path represents net work input required. Greater spacing between actual and ideal paths quantifies irreversibility losses.
HVAC Applications
T-S diagrams clearly show why real compressors require more work than ideal isentropic compression. Entropy generation during throttling through expansion devices appears as rightward movement. Inefficient evaporators and condensers show larger entropy increases compared to ideal heat exchange. System designers use T-S diagrams to identify the most inefficient components deserving improvement efforts. The diagram illustrates that total entropy must increase in all real processes according to the second law of thermodynamics, quantifying the minimum theoretical energy required for any heating or cooling operation.