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ABSTRACT
Current trends in the HVAC industry lead to increased air flowrates to improve air conditioner's efficiency compared to when testing standards were originally developed. However, such increases in air flowrate lead to a reduction in the enthalpy and temperature change across the heat exchanger coil, with a similar effect observed for the built equipment. In parallel, the dimensions of unitary equipment have increased leading to challenges when including current standard's inlet ductwork which recently became mandatory in the US. Based on our experience, different testingfacilities use different designs for inlet ductwork and air sampling to enable installation in legacy testingfacilities. This leads to differences in the measured performance between labs and can lead to "false testingfailures" caused by differences in testing method.
This paper presents the work that has been done as part of ASHRAE RP 1733 and 1743 to address these challenges on the equipment as well as on the component (heat exchanger) level. In general, achieving repeatable test results and accurate airside measurement requires either a large length for mixing andflow development or a shorter length at the expense of additional airside pressure drop.
(ProQuest: ... denotes formulae omitted.)
INTRODUCTION
ASHRAE RP 1743: ASHRAE and AHRI provide standards for designing test setup for HVAC units, but with limited guideline for inlet ductwork design. The purpose of this project is to develop a guideline for the inclusion in ASHRAE and AHRI standards that will reduce the risk of false testing failures and will increase reliability and integrity in testing results accross different laboratories. This project aims to reduce the overall height of the testing setup by reducing the length of the inlet duct while maintaining the equivalent power as of standard case.
ASHRAE RP 1733: Despite the importance of the air mixing process in psychrometric performance testing for accurate measurement of average air conditions, there are limited guidelines available for mixer design and evaluation, and TRP 1733 was designed to address these issues. Therefore, the goal of RP1733 is to propose air mixer designs and investigate their performance in terms of mixing effectiveness and pressure drop, followed with guidelines for the inclusion in the applicable standards and regulations. In addition, the outcome of this project will provide proven design recommendations for accurately...