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

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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.

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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

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.

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).

Δ :

Difference.

ω :

Humidity ratio.

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Authors and Affiliations

  1. Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr/Isfahan, Iran

    Mohammad Ali Fazilati

  2. Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran

    Ali Akbar Alemrajabi & Ahmad Sedaghat

Authors
  1. Mohammad Ali Fazilati
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  2. Ali Akbar Alemrajabi
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  3. Ahmad Sedaghat
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Correspondence to Mohammad Ali Fazilati.

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Fazilati, M.A., Alemrajabi, A.A. & Sedaghat, A. Natural convection liquid desiccant loop as an auxiliary air conditioning system: investigating the operational parameters. Heat Mass Transfer 54, 903–913 (2018). https://doi.org/10.1007/s00231-017-2191-4

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