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Incorporating novel heat recovery units into an AHU for energy demand reduction-exergy analysis

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Abstract

The building sector is the major energy consumer, accounting for over 40% of global energy demand. Heating and cooling together with domestic hot water energy consumption are estimated to account for 60% of the required energy for buildings’ maintenance and operation. Energy recovery is a suitable technique to tackle high energy consumption in the building. In this study, a new layout of heat recovery units installation (i.e., primary and secondary) is investigated. The main objective of this study is to reduce energy consumption in an air handling unit through the exergy analysis. Owing to adding heat recovery units, cooling and heating coil loads reduced by 7.8% and 43%, which in turn decreased the total required load of AHU by 17.84%. From the viewpoint of the second law and based on the results, incorporating the primary and secondary heat recovery units into the base AHU in hot and dry climate regions led to decrease in the total irreversibility up to 26.29%, while in hot and humid climate this figure is 14.25%. Consequently, the positive effect of using heat recovery units in the hot and dry climate region is superior to the hot and humid one.

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Abbreviations

Ex:

Exergy \(\left( {\text{J}}\,{\text{kg}}^{-1} \right)\)

h :

Enthalpy \(\left( {\text{J}}\,{\text{kg}}^{-1} \right)\)

\(h_{\text{s}}\) :

Supply air enthalpy

IR:

Irreversibility ratio

IRV:

Irreversibility (W)

\(\dot{m}\) :

Mass flow rate \(\left( {\text{kg}}\,{\text{s}}^{-1} \right)\)

\(\dot{m}_{\text{s}}\) :

Supply air mass flow rate \(\left( {\text{kg}}\,{\text{s}}^{-1} \right)\)

\(\dot{m}_{\text{f}}\) :

Fresh air mass flow rate \(\left( {\text{kg}}\,{\text{s}}^{-1} \right)\)

\(\dot{m}_{\text{r}}\) :

Return air mass flow rate \(\left( {\text{kg}}\,{\text{s}}^{-1} \right)\)

\(\dot{m}_{\text{c}}\) :

Cold water mass flow rate \(\left( {\text{kg}}\,{\text{s}}^{-1} \right)\)

PENR:

Percent of energy recovery

PEXR:

Percent of exergy recovery

Q :

Power (W)

\(Q_{\text{S}}\) :

Sensible heat transfer rate

\(\vartheta\) :

Specific volume \(\left( {\text{m}}^{3}\, {\text{kg}}^{-1} \right)\)

RPR:

Required power ratio

s :

Entropy \(\left( {\text{J}}\,{\text{kg}}^{-1}\,{\text{K}}^{-1} \right)\)

SER:

Second efficiency ratio

T :

Temperature (K)

\(T_{\text{ax}}\) :

Air temperature at the condensation point (K)

\(T_{\text{o}}\) :

Ambient temperature (K)

\(T_{\text{s}}\) :

Supply air temperature (K)

\(\varphi\) :

Relative humidity

\(\omega\) :

Humidity ratio \(\left( {\frac{{{\text{kg}}_{\text{v}} }}{{{\text{kg}}_{\text{a}} }}} \right)\)

\(\varepsilon\) :

Effectiveness

ai:

Air inlet

ao:

Air outlet

cc:

Cooling coil

ci:

Chilled water inlet

co:

Chilled water outlet

cond:

Condensation

cw:

Chilled water

h:

Heating coil

hi:

Hot water inlet

ho:

Hot water outlet

hw:

Hot water

max:

Maximum

min:

Minimum

mix:

Mixing box

o:

Ambient

pr:

Primary heat exchanger

r:

Conditioned space

se:

Secondary heat exchanger

t:

Total

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Authors and Affiliations

  1. Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

    Rasool Kalbasi

  2. Department of Mechanical Engineering, Kermanshah University of Technology, Kermanshah, Iran

    Amin Shahsavar

  3. Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam

    Masoud Afrand

  4. Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam

    Masoud Afrand

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  1. Rasool Kalbasi
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  2. Amin Shahsavar
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  3. Masoud Afrand
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Correspondence to Masoud Afrand.

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Kalbasi, R., Shahsavar, A. & Afrand, M. Incorporating novel heat recovery units into an AHU for energy demand reduction-exergy analysis. J Therm Anal Calorim 139, 2821–2830 (2020). https://doi.org/10.1007/s10973-019-09060-4

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