A refrigerating system using R – 134a has a load of 20 kW. Limits of operating pressures are 750 kPa and 150 kPa. The refrigerant enters the compressor suction as superheated vapor at 0.14 MPa and – 10°C and exits at 0.75 MPa and 60°C. The refrigerant is cooled in the condenser to 24°C and 0.65 MPa. The refrigerant is then throttled to 0.15 MPa before the evaporator. Calculate the COP of the system.
Theory and Design for Mechanical Measurements
Measurement is a term that refers to analyzing a manufactured component regarding the degree of accuracy for dimensions, tolerances, geometric profile, roundness, flatness, smoothness, etc. Measurement always involves comparing the manufactured component or the prototype with a standard specimen whose dimensions and other parameters are assumed to be perfect and do not undergo changes with respect to time.Precisely in mechanical engineering the branch that deals with the application of scientific principles for measurements is known as metrology. The domain of metrology in general deals with various measurements like mechanical, chemical, thermodynamic, physical, and biological measurements. In mechanical engineering, the measurements are limited to mechanical specific such as length, mass, surface profile, flatness, roundness, viscosity, heat transfer, etc.
Basic principles of engineering metrology
Metrology is described as the science of measurement, precision, and accuracy. In other words, it is a method of measurement based on units and predefined standards.
Instructions:
- Demonstrates thorough understanding of the problem and precisely identifies and collects all
significant data and requirements of the problem. - A realistic diagram/illustration of the physical system indicating relevant information in the figure.
- Assumptions and approximations are sufficiently and clearly stated.
- Selects an effective and efficient problem – solving strategy that will lead to a valid and accurate
solution to the problem. Relevant physical laws and principles were identified. Realistic constraints were
considered and well-defined before solutions are implemented. - Accurately implements the problem – solving strategy to achieve a valid and accurate solution. No
errors are present. - Provides concise and insightful justification to the solution using appropriate data.
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