98 lines
1.4 KiB
Markdown
98 lines
1.4 KiB
Markdown
---
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tags:
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- destiny/uncertain
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- topic/construction/electrical
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- type/encyclopedia
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title: HVAC Calculations
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---
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# HVAC Calculations
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## Units
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### British Thermal Unit
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Unit of **heat energy**
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There are several definitions of the Btu,
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HVAC uses the IT definition,
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abbreviated Btu<sub>IT</sub>
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$$
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\begin{align*}
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1~\text{Btu}_\text{IT} &\equiv \left( 4.1868 \times 453.59237 \times{\frac{5}{9}} \right)~\text{J} \\
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&\approx 1055.056~\text{J}
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\end{align*}
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$$
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More common than Btu itself is
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thousand British thermal units per hour (MBH),
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a unit of **power**.
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$$
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\begin{align*}
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1~\text{MBH} &\equiv 1000~\text{Btu/hr} \\
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&\approx 3.412~\text{W}
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\end{align*}
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$$
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### Ton of Refrigeration (TR or TOR)
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Unit of **power**
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> [!info] Also Known As
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> * refrigeration ton (RT)
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> * ton (refrigeration)
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$$
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\begin{align*}
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1~\text{TR} &\equiv 12000~\text{Btu}_\text{IT}/\text{h} \\
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&\approx 3516.853~\text{W}
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\end{align*}
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$$
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### Cubic Feet per Minute (CFM)
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Unit of **volumetric flow**.
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## Measures
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### Airflow
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External static pressure (ESP)
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measured in inches of water (IN WC) "water column inches"
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### Heating/Cooling Capacity
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* Tons (refrigeration)
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* MBH
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* Entering air temperature (EAT)
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* Leaving air temperature (LAT)
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* Mixed air temperature (MAT)
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* Latent heat
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* Sensible heat
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* Sensible -> dry bulb
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* Latent -> wet bulb
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#### ???
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* OSA EAT (F)
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* EXH EAT (F)
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* IN S.L.
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* OUT ALT.
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##### Ratings
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* MERV
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* SEER2
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* HSPF2
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### Efficiency
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* η (eta)
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* ISMRE
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