Miklos Kassai

Performance investigation of liquid-to-air membrane energy exchanger under low solution/air heat capacity rates ratio conditions

Liquid-to-air membrane energy exchanger is a novel membrane base energy exchanger, which allows both heat and moisture transfer between air and a salt solution. The heat and mass transfer performance of a single one is significantly dependent on two dimensionless parameters: number of heat transfer units and the ratio of heat capacity rates between solution flow and air flow (Cr*). The performance of liquid-to-air membrane energy exchanger under high Cr* (i.e. Cr* ≥ 1) has been comprehensively investigated experimentally and numerically in previous research. In this study, the effectiveness of a small-scale liquid-to-air membrane energy exchanger under low Cr* conditions (i.e. Cr* < 1) is experimentally tested. Good agreement between the experimental and numerical results is achieved under low Cr* cases. Practical application : The ideal energy exchanger is one that can transfer both heat and moisture because during hot and humid conditions such an exchanger is capable of transferring up to four times as much energy as an exchanger that can transfer sensible heat only. It is beneficial if the exchanger can transfer heat and moisture also between remote supply and exhaust airstreams, as this may minimize the ducting required and reduces contaminant transfer from one airstream to the other. This is very important for applications such as hospitals, laboratories, and manufacturing facilities, where slight cross contamination can cause serious health effects.

Experimental investigation on the effectiveness of sorption energy recovery wheel in ventilation system

ABSTRACT The object of this research was to investigate the effectiveness of sorption energy exchanger and the impact of the operational and thermal environmental conditions on their efficiency under steady-state conditions. To achieve this object, a test facility was installed into the Indoor Air Quality and Thermal Comfort Laboratory of BUTE University. A molecular 3Å sieve sorption wheel with high latent effectiveness is integrated into the experimental setup. In this study, the correlation between the sensible, latent, total effectiveness under different ambient air temperature and humidity values and different rotational speeds of the wheel is investigated in detailed by experimental tests.

Experimental investigation of carbon dioxide cross-contamination in sorption energy recovery wheel in ventilation system:

The aim of this research was to investigate the scale of carbon dioxide recirculation in rotary energy wheel operated in air handling units. To achieve this objective, a test facility was installed into the indoor air quality and thermal comfort laboratory of BUTE University. A newly developed molecular 3 Å sieve sorption wheel with high humidity transfer efficiencies is integrated into the experimental setup. In this research study, carbon dioxide cross-contamination rate from the exhaust side into the supply side in sorption regenerative air-to-air rotary energy exchanger was conducted by experimental tests. During the study, the correlation between the carbon dioxide cross-contamination, different rotational speeds of the wheel and different volume flow rates of supply air were also investigated in detail. Based on the results, a rotation speed diagram – carbon dioxide cross-contamination diagram – is plotted which can be very useful for researchers, developers and building service engineers in practice. Practical application: The most perfect energy exchanger can transfer both heat and moisture, thus providing a pleasant indoor air quality in the conditioned space. It is beneficial if the exchanger can transfer heat and moisture between the supply and exhaust airstreams, thereby minimizing the capacity and energy consumption of the required auxiliary heater and humidifier. The auxiliary energy reduction can be especially high if the sorption material of the energy wheel is of type 3 Å molecular sieve that has an extremely high humidity transfer capacity. The disadvantage of the rotary energy recovery is the cross-contamination from the exhaust air to the supply air. This is very important because in places such as offices, schools, public institutions, carbon dioxide cross-contamination can cause degradation of indoor air quality.

Experimental Effectiveness Investigation of Liquid-to-air Membrane Energy Exchangers under Low Heat Capacity Rates Conditions

The liquid-to-air membrane energy exchanger is a novel membrane base energy exchanger that allows both heat and moisture transfer between air and a salt solution using a membrane. The heat and mass transfer performance of a single one is significantly dependent on two dimensionless parameters: number of heat transfer units and the ratio of heat capacity rates between solution flow and airflow (Cr*). In this study, the effectiveness of a small-scale liquid-to-air membrane energy exchanger under low Cr* conditions (i.e., Cr* < 1) that has been not investigated previously is experimentally and numerically tested.