Refrigeration Lab
Liquid desiccant dehumidification system
Cross-flow mechanical draft wet cooling tower
Visulalization of heat and mass transfer process
Design and Development of Hybrid Type SolarDriven Liquid Desiccant Air Conditioning System:
Objectives:
- To develop a thermal model for simulating the performance of dehumidifier and regenerator and evacuated U- tube solar collector.
- To design the various components of the hybrid type solar driven liquid desiccant air conditioning system for a cooling capacity of 7 kW.
- To study the effects of operating parameters such as desiccant to air mass flow rate ratio, ambient relative humidity and dry bulb temperature, desiccant solution concentration and temperature, moisture removal rate on the performance of the system.
- To investigate the properties of liquid desiccant materials such as LiCl, LiBr, KCOOH and CaCl2 according to humid subtropical climate.
- To analyse the LiCl blend and LiBr blend properties for performance improvement of the existing dehumidification system.
- To study the performance of evacuated tube solar collectors according to humid subtropical climate by varying the mass flow rate of desiccant solution and using different desiccant materials at various ambient conditions.
- Validation of numerical results with experimental data
- To carry out the economic analysis of the developed setup to find its viability and sustainability.
Liquid Desiccant Air Conditioning System:
In hot and humid climates, to maintain comfort conditions, remove air borne contaminants and protect sophisticated equipment’s, dehumidification of ambient air is crucial. Before 20th century, for dehumidifying the ambient air, traditional vapour compression and vapour absorption based air conditioning systems were widely used. These type of dehumidification processes consume more power and possess high energy demand. To overcome this issue, in recent years, desiccant based air conditioning system has been introduced.
Desiccant based air conditioning system is classified as solid desiccant based air conditioning system and liquid desiccant based air conditioning system. In recent years, compared to solid desiccant based air conditioning system, liquid desiccant based air conditioning system is became advantageous due to less air side pressure drop, less maintenance, operational flexibility and utilization of low- grade thermal energy sources such as solar or waste heat for the regeneration of liquid desiccant. Therefore, solar driven liquid desiccant based air conditioning system is chosen for the present investigation.
Dehumidifier, regenerator and solar collector are the key components of solar driven liquid desiccant based air conditioning system. Dehumidifier works based on the principle of condensation whereas regenerator works based on the principle of evaporation. In the dehumidifier, desorption of water vapor takes place from ambient air to the liquid desiccant whereas in the regenerator, absorption of water vapor takes place from the liquid desiccant to the ambient air. During absorption and desorption processes, simultaneous heat and mass exchange occurs in between the air and the liquid desiccant. The driving force for heat exchange is the temperature difference whereas for the mass exchange, it is the vapor pressure difference between the air and the desiccant. These driving forces depend upon the changes in local temperature and vapour pressure at the air – desiccant interface.
Milestones Achieved:
- Developed a thermal model for analyzing the simultaneous heat and mass transfer processes occurring in a counter flow packed chamber and to predict the performance of the structured packing chamber.
- Developed a 3D numerical model for evaluating the performance of the individual evacuated U – tube solar collector as well as for the whole solar collector system.
- Designed and fabricated a liquid desiccant dehumidification/regeneration system of 18 kW capacity.
- Designed and fabricated evacuated U – tube solar collector system for achieving the working fluid temperature difference of 35οC.
- Performed a detailed experimental study on liquid desiccant dehumidification/regeneration system and evacuated U – tube solar collector system at different operating and ambient conditions.
- Validated the developed thermal models with the experimental data for both the dehumidification/regeneration system and also for the evacuated U – tube solar collector system.
- Carried out energy and exergy analyses of the liquid desiccant dehumidification/regeneration system and the evacuated U – tube solar collector system.
- Introduced the concept of entransy for heat and mass transfer processes and analyzed the entarnsy dissipation due to heat and mass transfer processes between the ambient air and the liquid desiccant.
- Proposed a simplified thermodynamic model for predicting the heat and mass transfer coefficients along the cross flow packed chamber by considering the effect of Lewis number.
Gallery
Design and development of Evacuated U – tube solar collectors
Numerous studies reported on analysing the performance of the evacuated tube and flat plate type solar collectors were concluded that evacuated tube type solar collectors were more efficient compared to flat plate type solar collectors. Several types on evacuated tube solar collector configurations viz. U – type, H – type, T – type, heat pipe type, etc. have been reported for various solar thermal utilization applications. Among these, owing to simplicity in design and lower investment cost factors, evacuated U – tube solar collector is considered for present investigation. The solar radiation incident on the outer glass surface of the evacuated tube is transferred to the inner glass tube through radiative heat transfer and then the heat is absorbed by the U – tube. From U – tube, the heat is exchanged to the working fluid.
An experimental investigation for predicting the performance of evacuated U – tube solar collector is presented. A simplified numerical model is developed for predicting the working fluid outlet temperature of a single evacuated U – tube solar collector and also for the whole solar collector system. The model predictions are compared with the experimental data and noticed a good agreement exists between them. It is observed from the experimental and numerical analyses that evacuated U – tube solar collector manifolds connected in series provides higher temperature rise of working fluid at higher solar intensities and lower working fluid inlet temperatures and flow rates. The working fluid transition time in an evacuated U – tube solar collector is defined for analysing the time taken by a working fluid to attain a steady state condition. Based on experimental analysis, three empirical correlations for predicting working fluid transition time, energy efficiency and exergy efficiency are developed as the function of operating parameters and ambient temperature.
Milestones Achieved:
- Performance of evacuated U – tube solar collector system is studied experimentally.
- Proposed a simplified thermal model for evacuated U – tube solar collector systems.
- Defined working fluid transition time for an evacuated U – tube solar collector.
- Estimated energy and exergy efficiencies of an evacuated U – tube solar collector.
- Developed correlations for analysing the performance of the solar collector.
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Techno – Economic assessment of Water Cooled and Air Cooled Condenser Based Air Conditioning Plants for Humid Subtropical Region
Objectives:
The present work aims at performance analysis of both water cooled condenser (WCC) and air cooled condenser (ACC) A/C plant as well as making comparison between WCC and ACCs under various atmospheric conditions.
The major objectives of the present work are:
- To investigate the cooling tower performance parameters like range, approach and efficiency, water loss, COP, power consumption per ton of refrigeration (TR) on regular intervals of time (8 AM-6 PM) in selected days for a WCC A/C plant.
- To investigate COP, power consumption per TR on regular intervals of time (8 AM-6 PM) in selected days for an ACC A/C plant.
- To compare the performance analysis of WCC and ACC A/C plant on regular intervals of time (8 AM-6 PM) in selected days.
An experimental investigation on both air cooled and water cooled condenser based air conditioning (A/C) plants have been carried out in order to estimate which is the best option for humid subtropical climate. The performances of both the plants in terms of COP for mechanically driven refrigeration systems, peak power consumption, Seasonal load demand and life cycle cost analysis have been evaluated. Extensive experimental studies on mechanical draft cooling towers have been carried out over a period of 4 months (June-September). During this analysis, it was found that an average of 1.28 kW/TR and 0.68 kW/TR overall power is consumed annually for air cooled and water cooled condenser based A/C plants. The chiller load variations are ranging from 100% in summer season to 70% in winter season. It was noticed that maximum period, the chillers use to operate at 85% load. Moreover, for a period of 15 years plant life the overall cost (Initial cost, maintenance cost and operating cost) of air cooled condenser A/C plant is found to be Rs. 5, 73, 18,803 /- more than water cooled condenser based A/C plants. The study can be used as a reference tool for the economic investigation of any A/C plants with large capacities of above 1000 TR.
Milestones Achieved:
An experimental investigation on both air cooled and water cooled condensers air conditioning (A/C) plants in terms of cooling tower approach, range and efficiency, water loss, overall power consumption, compressor power consumption, coefficient of performance and life cycle cost analysishave been presented in order to estimate which is the best option for a humid subtropical region like Guwahati.
Water cooled condenser A/C plant
Performances of cross flow induced mechanical draft cooled towers employed in a water cooled condenser air-conditioning plant in terms of approach, range and efficiency have been presented over a period of four months. Average water loss per hr per TR refrigeration has been estimated according to the humid subtropical region. It was observed that the peak hour (2 pm) water loss was about 3.4 lit/hr-TR corresponding to 80 % of ambient relative humidity recorded on 22/08/2013. The average values of cooling tower range, approach and efficiency during the test period were about 2.6 °C, 4.6 °C and 35% respectively. Variation of psychometric properties from June to September 2013 has been presented using psychometric chart. Employing a simple cooling coil arrangement of having a dew point temperature of about 8-12 °C, the average cost of condensing per lit of water is estimated to Rs.0.75. During this analysis it is noticed thatoverall power consumption and compressor power consumption at 2:00 pm was about 0.76 kW/TR and 0.65 kW/TR corresponding to 35°C ambient temperature on 18/09/2013. In addition it is observed that COP at 2:00 pm was about 5.4 corresponding to 32°C ambient temperature on 17/08/2013.
Air cooled condenser A/C plant
Performances of air cooled condenser air-conditioning plant in terms of overall power consumption, compressor power consumption and coefficient of performance have been investigated. During this investigation it was found that overall power consumption and compressor power consumption at 2:00 pm are about 1.38 kW/TR and 1.24 kW/TR corresponding to 35°C ambient temperature on 18/09/2013. In addition it is observed that COP at 2:00 pm is about 3.3 corresponding to 32°C ambient temperature on 17/08/2013. Moreover the amount of power consumed by a cooling fan is observed to be 1.4 kW.
Comparison between WCC and ACC based A/C plant
During this study peak power consumption, seasonal load demand and life cycle cost analysis have been evaluated. It was found that an average of 1.34 kW/TR and 0.65 kW/TR overall power is consumed annually for air cooled condenser (ACC) and water cooled condenser (WCC) A/C plants. Also the load variations are ranging from 100 % in summer season to 70 % in winter season in addition it is noticed that maximum period the chillers use to operate at 85% load. Moreover it is observed that for a period of 15 years plant life, the cost of ACC is found be Rs. 5, 73, 18, 803/- more than WCC. The study which carried out on both ACC and WCC A/C plants can be used as a reference for economic analysis of any A/C plants of huge capacities also the experimental studies which are carried on COP have realistic significance in addition it may provide new guidance for the performance improvement and optimization of chiller.
Completed project
- Energy Auditing in Cadila RAC plants (2017), sponsored by M/s. Cadila Pharmaceutical
Ongoing project:
- Design and development of solar driven liquid desiccant air conditioning system (2016 – 2018) sponsored by Engineering section IITG (Project No.: IITG/ENGG/15/NIQ/09).