Heat and Mass Transfer

, Volume 54, Issue 3, pp 903–913 | Cite as

Natural convection liquid desiccant loop as an auxiliary air conditioning system: investigating the operational parameters

  • Mohammad Ali Fazilati
  • Ali Akbar Alemrajabi
  • Ahmad Sedaghat
Original
  • 30 Downloads

Abstract

Liquid desiccant air conditioning system with natural convection was presented previously as a new generation of AC systems. The system consists of two three-fluid energy exchangers namely absorber and regenerator in which the action of air dehumidifying and desiccant regeneration is done, respectively. The influence of working parameters on system performance including the heat source and heat sink temperature, concentration of desiccant solution fills the system initially and humidity content of inlet air to regenerator is investigated experimentally. The heat source temperatures of 50 °C and 60 °C, heat sink temperatures of 15 °C and 20 °C and desiccant concentrations of 30% and 34%, are examined here. The inlet air to regenerator has temperature of 38.5 °C and three relative humidity of 14%, 38% and 44%. In all experiments, the inlet air to absorber has temperature of 31 °C and relative humidity of 75%. By inspecting evaluation indexes of system, it is revealed that higher startup desiccant concentration solution is more beneficial for all study cases. It is also observed although the highest/lowest temperature heat source/heat sink is most suitable for best system operation, increasing the heat source temperature should be accompanied with decreasing heat sink temperature. Using drier air stream for regenerator inlet does not necessarily improve system performance; and the air stream with proper value of humidity content should be employed. Finally after running the system in its best working condition, the coefficient of performance (COP) reached 4.66 which verified to be higher than when the same air conditioning task done by a conventional vapor compression system, in which case the COP was 3.38.

Abbreviations

AC

Air conditioning

CC

Cooling capacity (W)

COP

Coefficient of performance

HR

Humidity ratio (g rmoisture .kg air −1 )

H/M

Heat and mass

IAQ

Indoor air quality

LAMEE

Liquid to air membrane energy exchanger

LDAC

Liquid desiccant air conditioning

MRR

Moisture removal rate

PIV

Particle image velocimetry

RAMEE

Run around membrane energy exchanger

RH

Relative humidity; mass of water vapor in air related to its saturation condition

SHR

Sensible heat ratio

VCS

Vapor compression refrigeration system

Subscripts

abs

Absorber (dehumidifier).

amb

Ambient condition.

cw

Cold water.

db

Dry bulb.

deh

Dehumidifier.

comp

Air compressor.

down

Lower junction of the loop.

ev

Evaporator.

hw

Hot water.

in

Inlet fluid flow.

lat

Latent.

out

Outlet fluid flow.

reg

Regeneration.

sen

Sensible.

tot

Total.

up

Upper junction of the loop.

w

Water.

Nomenclature

A

Study case 1.

B

Study case 2.

c

Specific heat capacity (kJ.kg −1 .K −1 ).

C

Concentration (kg salt .kg sol −1 ).

E

Power(kW).

\( \dot{m} \)

Mass flow rate (kg.s −1 ).

P

Pressure (kPa).

\( \dot{Q} \)

Heat transfer rate (W).

T

Temperature ( o c).

Greek letters

Δ

Difference.

ω

Humidity ratio.

Notes

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.Department of Mechanical Engineering, Khomeinishahr BranchIslamic Azad UniversityKhomeinishahr/IsfahanIran
  2. 2.Department of Mechanical EngineeringIsfahan University of TechnologyIsfahanIran

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