FACULTY OF ENGINEERING AND SUSTAINABLE DEVELOPMENT Department of Building Engineering, Energy Systems and Sustainability Science Key factors and problems in the performance of kitchen ventilation systems Explorative review study Álvaro Ros Hueda 2020 Student thesis, Advanced level (Master degree, one year), 15 HE Energy Systems Master Programme in Energy Systems Supervisor: Alan Kabanshi Assistant supervisor: Roland Forsberg Examiner: Magnus Mattsson ABSTRACT Regarding the great importance of a good working environment, in this research, ventilation systems installed in kitchens of restaurants were studied in order to avoid problems and to understand the key factors that can influence on the performance of the system. The results obtained were taken into account to provide some recommendations to a real ventilation system of a restaurant called Pastaria in Gävle (Sweden). This concrete ventilation system was not performing good, and some calculations based on the kitchen design were made trying to offset the problem. A large number of scientific studies related to restaurant kitchen hoods and ventilation systems were used to get the findings. These articles were obtained from scholar web databases. The main problem found in kitchen hoods is the inadequate exhaust airflow. The minimum required airflow varies depending on the size and shape of the hood. Keil et al. (2004) found in their research that only 39% and 24% of the studied hoods met the minimum recommended airflow from ACGIH and ASHRAE guidelines, respectively. Other key factors found are related to the kitchen design. The kitchen hood is recommended to have incorporated a capture hood covering all the burners. Side panels can be employed to increase the capture and containment. High efficiency filters and rigid ducts are also recommended. The cleaning of the ventilation ducts is also an important factor, they are recommended to be cleaned between 1 to 9 years depending on the activity of the kitchen. Thus, key factors such as disturbing airflows and the presence/movement of the cooks can disturb the kitchen hood performance. A very effective solution, isolating the fumes below the hood, that is getting developed is the installation of an inclined air curtain from the cooking surface. Related to the kitchen hood and the ventilation system of the Pastaria restaurant. Some measurements and information were obtained in a visit to the restaurant. After calculations, it was obtained based on the kitchen design that is required a minimum airflow of 4 140 m3/hour. In order to do that, the heat exchanger Swegon Silver C RX, installed in the system, requires a minimum size of 11/12. The distribution of the kitchen appliances in this restaurant seems to be correct. However, a future study in order to see if there are disturbing airflows affecting the kitchen hood performance must be carried out. If after checking all recommendations the performance of the kitchen hood is not good enough yet, an inclined air curtain may be installed due to their great effectiveness against problems of hoods. In conclusion, it was clearly obtained that a correct kitchen distribution design and calculations must be done for each restaurant in order to install the most adequate kitchen hood with the best characteristics. This way, fumes, odors, moisture and particles will be easily exhausted allowing a better environment out of risks to the establishment and customers health. Keywords Restaurant kitchen ventilation, kitchen hood, ventilation system, airflow, air quality, heat exchanger, pressure drop, ventilation ducts, hood performance and efficiency. i ii PREFACE This master thesis has been possible thanks to: My parents Ricardo and Teresa, whose unconditional support in good and bad times is the basis of my success. My sister Irache, the best personal stylist I could ever have. My girlfriend Nuria, whose delicious meals gave me the strength to carry on. My aunt Carmen, for her great evolution with new technologies to be able to make video calls when missing me. My mates from the Erasmus program, for our healthy competitiveness in all 3.5 “beerpong” tournaments, and Yahtzee and frisbee games. My friends from Estella, for allowing me to belong to the group “Bromeros”. iii NOMENCLATURE Symbol Description Unit NV Natural ventilation - MV Mechanical ventilation - HV Hybrid ventilation - IAQ Indoor air quality - ACGIH American Conference of Governmental Industrial Hygienists - ASHRAE American Society of Heating, Refrigerating and Air- - Conditioning Engineers 3 Qhood Volumetric flow through the hood m /h Vair Exhaust air velocity m/s A Extraction area m2 C&C Capture and Containment - DCV Demand control ventilation - HRV Heat recovery ventilation - DMF Deposited particle mass flux - UFP Ultrafine particles - ODA Outdoor air - IDA Indoor air - EA Exhaust air - iv TABLE OF CONTENTS 1. INTRODUCTION ................................................................................................ 1 1.1 Background .........................................................................................................5 1.2 Aims and limitations ............................................................................................7 2. METHOD .......................................................................................................... 8 3. RESULTS AND DISCUSSION................................................................................ 9 3.1 Reviewed articles ................................................................................................9 3.1.1 Operational problems .............................................................................................................. 14 3.1.2 Design problems ....................................................................................................................... 16 3.1.3 Cleaning problems .................................................................................................................... 20 3.1.4 Disturbing airflow problems ..................................................................................................... 22 3.1.5 Technical solutions ................................................................................................................... 24 3.2 Calculations for the current kitchen hood ........................................................... 26 3.3 Discussion ......................................................................................................... 29 4. CONCLUSION ...................................................................................................33 4.1 Study results ..................................................................................................... 33 4.2 Outlook ............................................................................................................. 34 4.3 Perspectives ...................................................................................................... 35 5. REFERENCES ....................................................................................................36 v FIGURES INDEX Figure 1. Basic components of a local exhaust system. ................................................... 4 Figure 2. Styles of Local Kitchen Exhaust Hoods (ASHRAE, 2015). ................................... 5 Figure 3. Pastaria restaurant. ........................................................................................... 6 Figure 4. Kitchen view of the Pastaria restaurant. ........................................................... 7 Figure 5. Proportion of Hoods Meeting the Airflow Performance Guidelines (Keil et al., 2004). .............................................................................................................................. 15 Figure 6. Schematic of 21 hood shapes studied (Zhao et al., 2013)............................... 17 Figure 7. Schematic of six side panels studied (Zhao et al., 2013). ................................ 17 Figure 8. Schematic of two exhaust duct arrangements studied (Zhao et al., 2013). ... 18 Figure 9. Comparison of the totally deposited particle mass in the duct for different cases (Zhao and Chen, 2006). ......................................................................................... 22 Figure 10. Comparison of the accumulation time in the duct for different case (Zhao and Chen, 2006). ............................................................................................................. 22 Figure 11. The ventilation system principle diagram (Liu et al., 2020). ......................... 25 Figure 12. Area calculated between the hood and the cooking surface. ...................... 27 Figure 13. Operation diagram of the minimum heat exchanger size required (Swegon Group AB, no date). ........................................................................................................ 29 vi TABLES INDEX Table 1. Summary of reviewed articles. ......................................................................... 10 Table 2. Typical exhaust flow rates by cooking equipment category for listed type I hoods (ASHRAE, 2015). ................................................................................................... 28 vii viii 1. INTRODUCTION Ventilation is the process of diluting the air inside a building by extraction of old air or injection of fresh air (Sandberg, Kabanshi and Wigö, 2020). Indoor air is polluted from cooking, smoke, formaldehyde and other pollutants that can cause allergies, smells and diseases (Bluyssen,