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MANE-4740 Thermal and Fluids Engineering Laboratory

Results Homework 1 – AC Lab

Fall 2024

For each of the following groups of data or computed quantities, organize your results into plots, tables, or other figures as you think best (unless told to plot them a specific way). This will help you prepare for writing your technical report. Please show your work.

Note on Formatting: For this assignment, it is not necessary to write out the problem statement. You may copy the statement and paste it into your homework. Otherwise, homework should be formatted as described in the syllabus.

Note on Uncertainty: It is not necessary to calculate the uncertainty for this homework assignment.

Note on Properties: Use properties from a recognized thermodynamics textbook. The Moran & Shapiro textbook is recommended. Online property tables, especially for R-134A, are unreliable.

Note on .pdf Files: PDFsam Basic is a free and open-source application that can be used to split, merge, rotate, and otherwise organize .pdf files.

Operating Conditions: The experiment was run under 2 different sets of operating conditions:

A. First set of operating conditions (without condensation):

•    100% fresh air

•    The temperature on inlet of the air side of the evaporator at about 30°C

B. Second set of operating conditions (with condensation):

•    (some amount)% re-circulated air and [100% - (some amount)%] fresh air

•    Humidification system turned on (3kW heating power)

•    A total air flow rate through the evaporator of about 0.15 kg/sec

•    About 60% relative humidity on inlet of the air side inlet of the evaporator

1.   Investigate the function of the evaporator (Operating Condition A)

a.    Compare the heat transferred into the refrigerant versus the heat transferred out of the air. In theory, these values would be equal, but in practice they are not.

b.    Compare the overall heat transfer coefficient (U) and NTU value calculated using the LMTD method, versus the overall heat transfer coefficient (U) and NTU value determined via the E − NTU method (i.e. you will find two different values for U and two different values for NTU). Both of these methods will use your experimental data, soneither is a true “literature” value, but it is useful to compare their results to each other.

2.    Investigate the function of the compressor (Operating Condition A). Determine the coefficient of performance (COP) of the refrigeration cycle in two ways, one that incorporates the mechanical efficiency of the compressor (using the measured electrical power input), and one that excludes the mechanical efficiency (using the enthalpies of the R134a).

3.    Investigate the unit’s dehumidification ability (Operating Condition B). Use the measurements of the air mass flow rate and humidity before and after the evaporator to perform a conservation of mass and energy analysis to predict the condensate flow rate (i.e. how fast water is condensing out of the air in the duct). This is a measure of the system’s ability to dehumidify the airstream. Compare this to the steam added to the duct flow (use the measurements of the air mass flow rate and humidity before and after the steam addition).

4.    Investigate the unit’s overall function (Operating Condition B). Compare the measured properties of therecirculated air + fresh air mixture after the damper (in the region of thermometers 1 and 2), with those properties calculated using an energy balance and mass balance analysis on the mixing of therecirculating air (in the region of thermometers 9 and 10) and fresh air (in the region of thermometers 11 and 12). The properties to compare are dry bulb temperature and specific humidity.