Thermodynamics question about mass flow rate in an air conditioning unit?

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Discussion Overview

The discussion revolves around estimating the temperature of mixed air in an air conditioning unit, specifically when fresh air at 10°C is mixed with warm air at 30°C, given a mass flowrate ratio of 1.6. Participants explore assumptions and methods related to thermodynamic principles in this context.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Homework-related

Main Points Raised

  • One participant proposes estimating the mixed air temperature based on the mass flowrate ratio and temperature difference, while expressing uncertainty about their approach.
  • Another participant suggests calculating energy in and energy out using the specific heat of air as a method to determine the mixed temperature.
  • A different viewpoint mentions assuming constant specific heat versus temperature, indicating that this is a typical approach for high school-level problems.
  • There is a question raised about whether standard assumptions for heat engine and heat pump problems should always be applied.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the best method for estimating the mixed air temperature, and multiple approaches and assumptions are discussed without resolution.

Contextual Notes

Assumptions regarding specific heat and the applicability of standard assumptions in thermodynamic problems are mentioned but not fully resolved. The discussion reflects varying levels of complexity in the proposed methods.

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1. In an air conditioning unit fresh air at 10°C is mixed with warm air at 30°C. If the mass flowrate ratio of warm to fresh air is 1.6, estimate the temperature at which the mixed air leaves the air conditioner. State any assumptions made.


and also do you always make the air standard assumptions for ALL heat engine and heat pump problems?


my attempt was mdot/mdot = flowrate ratio = change in temperature but then I don't think that makes sense, any help?
 
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Such a correlation would aid in system design and allow the examination of a full range of refrigerant choices.


air conditioner
 
One way to do it would be to may be calculate the energy in and energy out based off the specific heat of the air.
 
Assume constant specific heat vs. temperature and it's a high school-level problem.
 

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