INVESTIGATION OF THE ENERGY RECOVERY POTENTIALS IN VENTILATION SYSTEMS IN DIFFERENT CLIMATES

The aim of this research study was to investigate the energy recovery potentials in ventilation systems under different climatic conditions. The well-known heating degree day from the literature was updated using the weather data of cities with different climates from the past 40 years. As the novelty of this research with the developed procedure drawn up in this study, the energetic possibilities of heat recovery under various climate and operating conditions may be examined in more detail and more realistically than with the methods and available information of current engineering practices. To achieve this long-term and high definition the weather data of several cities are processed in order to evaluate the possibilities of heat recovery on a daily and annual basis

Energy Performance Investigation of a Direct Expansion Ventilation Cooling System with a Heat Wheel

Climate change is continuously bringing hotter summers and because of this fact, the use of air-conditioning systems is also extending in European countries. To reduce the energy demand and consumption of these systems, it is particularly significant to identify further technical solutions for direct cooling. In this research work, a field study is carried out on the cooling energy performance of an existing, operating ventilation system placed on the flat roof of a shopping center, located in the city of Eger in Hungary. The running system supplies cooled air to the back office and storage area of a shop and includes an air-to-air rotary heat wheel, a mixing box element, and a direct expansion cooling coil connected to a variable refrigerant volume outdoor unit. The objective of the study was to investigate the thermal behavior of each component separately, in order to make clear scientific conclusions from the point of view of energy consumption. Moreover, the carbon dioxide cross-contamination in the heat wheel was also analyzed, which is the major drawback of this type heat recovery unit. To achieve this, an electricity energy meter was installed in the outdoor unit and temperature, humidity, air velocity, and carbon dioxide sensors were placed in the inlet and outlet section of each element that has an effect on the cooling process. To provide continuous data recording and remote monitoring of air handling parameters and energy consumption of the system, a network monitor interface was developed by building management system-based software. The energy impact of the heat wheel resulted in a 624 kWh energy saving and 25.1% energy saving rate for the electric energy consumption of the outdoor unit during the whole cooling period, compared to the system without heat wheel operation. The scale of CO2 cross-contamination in the heat wheel was evaluated as an average value of 16.4%, considering the whole cooling season.</jats:p

A Developed Method for Energy Saving Prediction of Heat-and Energy Recovery Units

AbstractIn heat and energy exchangers frosting decreases the effectiveness of the exchangers. In a previous research effectiveness data were investigated experimentally considering the frosting effect [1]. Using these tested effectiveness data and ambient temperature/enthalpy duration curves annual heating energy consumption of ventilation systems were predicted in three different climate European locations. During this investigation two common frosting protection techniques were also considered: outdoor air preheating and outdoor airflow bypassing (supply side closing). The evaluation shows the outdoor air preheating technique results higher energy saved than the supply side closing. Furthermore if the indoor air quality demands are lower using a sensible heat recovery unit is satisfactory and the investment cost is lower

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. </jats:p

Investigation of the thermal behavior and energy consumption of refrigeration systems

The object of this research study is to develop a thermal simulation model that can be used to investigate the thermal parameters of the refrigerant systems (with ON/OFF and PID control) used in cooling chambers. Moreover, the model was further developed which takes into account also the types of compressors, feeder, and control units used commonly in practice for energetic investigations. Using the measured energy consumption data obtained by experimental tests during the previous phase of this research work, the validation of the developed energy simulation model by MATLAB R2016a could be also achieved with good agreement. The MATLAB software seemed to be the most appropriate tool for numerical investigations on the energy consumption of refrigeration systems used in commercial cold stores and transient behavior of the indoor air temperature of the cold store, cooling energy performance and consumed energy to the goods stored in cold store.</jats:p