Central ventilation system with heat recovery as one of the measures to upgrade energy efficiency of historic buildings.

Transcription

1 Applied Mechanics and Materials Submitted: ISSN: , Vols , pp Accepted: doi: / Online: Trans Tech Publications, Switzerland Central ventilation system with heat recovery as one of the measures to upgrade energy efficiency of historic buildings. Viktor Pukhkal 1,a, Nikolay Vatin 2,b Vera Murgul 3,c 1 St. Petersburg State University of Architecture and Civil Engineering, 2-Krasnoarmejskaja ul. 4, St. Petersburg, , Russia 2,3 St. Petersburg State Polytechnical University, Politekhnicheskaya ul., 29, , Saint-Petersburg, Russia a pva1111@rambler.ru, b vatin@mail.ru, c october6@list.ru Keywords: Heat recovery ventilation, air-to-air plate heat exchanger; heat recovery unit; low energy building, energy efficiency, reconstruction. Abstract. Improving thermal shield in buildings and reducing energy consumption have become major problems to be solved for the recent decades. Natural ventilation accounts for nearly half of heat losses in existing buildings. A controlled heat recovery ventilation system makes it possible to reduce irrational heat losses and improve microclimatic comfort. A typical historic residential apartment building constructed before industrial times in Saint-Petersburg is subject of this article. Options of centralized controlled heat recovery ventilation systems for old historic apartment buildings in Saint-Petersburg are suggested in this article. Introduction The share of residential buildings appeared before 1920 in Saint-Petersburg accounts for 12,8%. A set of measures should be taken to achieve reduction of heat energy needed for residential building [1, 2]. These could be the following measures: thermal insulation of the building s envelope, recovery of heat from ventilation emissions wastewater disposal, heating systems optimization. Heat energy can be saved to a significant extent due to heat recovery in building ventilation system [3, 4, 5]. Sealing of buildings Sealing has a number of advantages: it reduces heat losses from weathering, it increases temperature of internal surfaces, it reduces moister content in structural members. However, if a ventilation system is not well-defined sealing of a building can cause a range of troubles [6, 7]. 1) Sealing is incompatible with natural ventilation and implies compulsory use of a controlled ventilation system to ensure standard air exchange rate. 2) Sealing hinders air from easy penetration into rooms that can cause increase in moisture content. When buildings are heated with water, moisture in rooms is less than it should be, however excessive moisture may have negative impact on microclimate. 3) The temperature of the surfaces of internal walls may be lower than the dew point, for instance, due to insufficient thermal insulation or thermal bridge. If there is a high level of sealing and airing or ventilation is not sufficient relative humidity will be increasing that may eventually result in condensate drop-out on the rather warm surfaces. 4) If the temperature of heating in rooms is decreased the air circulation reduces consequently (convection reduction), and it may in turn induce mold growth on badly ventilated surfaces in the cold outer corners. This problem can be solved using controlled ventilation system [8]. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-06/03/16,11:36:21)

2 1078 Advanced Materials and Processes IV Contemporary arrangement of ventilation systems in multi-storey buildings. Contemporary experience of ventilation system arrangement in multi-storey buildings implies the following types: - natural ventilation systems with natural air intake and recovery; - ventilation systems with natural air intake and mechanical air recovery; - ventilation systems with mechanical air intake and natural air recovery; - ventilation systems with mechanical air intake and recovery. It is possible to reduce heat consumption in buildings significantly only if heat air recovery ventilation system based on mechanical air intake and exhaust is applied. Such systems can be subdivided into two types centralized (central) and decentralized [9, 10]. It is reasonable to use a centralized ventilation system for an object under consideration. Let s take plate heat exchangers (Figure 1) or a system with heat transfer medium (Figure 1) [11] for heat recovery arrangement. Figure 1. Scheme of a mechanical centralized air intake and exhaust ventilation system with plate heat exchangers of the air recovered. 1 air intake device; 2 exhaust device; 3 heating device; 4 satellite-duct; 5 assembly exhaust duct; 6 air intake and exhaust system with plate heat exchangers; 7 incoming air duct; 8 fire damper: 9 exhaust shaft

3 Applied Mechanics and Materials Vols Figure 2. Scheme of a mechanical centralized air intake and exhaust ventilation system with heat transfer medium. 1 air intake device; 2 exhaust device; 3 heating device; 4 satellite-duct; 5 intake duct (outside a room); 6 heat recovery system with heat exchanger as a heat transfer medium; 7 exhaust system with heat exchanger as a heat transfer medium; 8 heat transfer duct; 9 circulator pump; 10 range hood with fan; 11 exhaust shaft; 12 fire damper A cross flow heat exchanger consists of aluminum plates which form a ductwork system. Heat in a heat exchanger is transferred between aluminum plates with the help of air steams with different temperatures. Exhaust air (in winter warm; in summer sometimes colder than outer air) goes through each second duct in a heat exchanger and heats its plates. Intake air goes through all the rest ducts and is heated (in summer it is cooled) when touching duct surfaces heated (cooled) by exhaust air. An example of an air intake and exhaust system with plate heat exchangers is given in the Figure 3 [12, 13, 14]. Figure 3. a) General view of a heat exchanger. b) Plate heat exchanger designed to recover heat from air in ventilation systems.

4 1080 Advanced Materials and Processes IV There is a negative factor emerging in the process of heat recovery which is possible condensation when moisture condenses out of the air. A heat recovery unit should be fitted with drip and condensate trays to detect and manage condensation process. With the low air temperature (minus С) a heat exchanger may be covered with ice. To avoid the problem of icing a heat exchanger is additionally equipped with a specific automatic system which allows a heat exchanger to be defrosted at regular intervals [7, 10]. A heat recovery system with intermediate heating medium is presented in the Fig. 4. Figure 4. A basic scheme of a heat recovery system with intermediate heating medium 1 air-heater in an intake system; 2 air-cooler in an exhaust system; 3 drip tray; 4 circulator pump; 5 three-way control valve; 6 expansion tank The system contains two heat exchangers placed in the area of exhaust and intake air steams interconnected with pipes. The system is filled in with non-freezing liquid which is heated by exhaust air and cooled by intake air. A heat exchanger placed in the area of exhaust air is supplied with an additional drip tray since there may be condensation which must be removed from a special tray into a waste water disposal system on a continuous basis [15, 16, 17]. Comparative performance analysis in respect to two types of heat recovery units is given below in the Table 1. Table 1. Comparative performance analysis in respect to two types of heat recovery units. Type of a heat recovery unit Performance («energy saving capacity»), % «dry» heat exchanger heat exchanger with condensation with recuperative heat exchangers with intermediate heating medium When arranging centralized ventilation systems in historic buildings being renovated the following is recommended: - for intake air supply air diffusers are installed in dwellings, exhaust units in kitchens, lavatories and bathrooms, a ductwork should be arranged within the area of dwelling rooms; - air extraction in historic buildings can be implemented through an existing attic duct system; - a supplementary duct designed to supply floors with intake air should be used to arrange outer heated air intake; - air ducts should be connected up on each floor through air locks or fire dampers. Summary A range of the problems should be solved in reference to mechanically forced intake and exhaust ventilation systems to be arranged in multi-storey residential buildings. Accordingly the following actions should be taken: to choose an appropriate air intake and recovery scheme, define output of intake and exhaust air fans, determine duct sections values required. Using mechanical air intake and exhaust ventilation system in multi-storey residential buildings requires creating new solutions for air ventilation arrangement. Controlled heat recovery ventilation system makes it possible to optimize a

5 Applied Mechanics and Materials Vols room climate (humidity level, percentage of СО2, prevent mold growth), as well as increase energy efficiency up to 30% of total heat consumption. References [1] M. Fehrm, W. Reiners, M. Ungemach: Exhaust air heat recovery in buildings, International Journal of Refrigeration, Volume 25, Issue 4, (2002), pp [2] A. S. Gorshkov, P. P. Rymkevich, D. V. Nemova, N. I. Vatin: Method of calculating the payback period of investment for renovation of building facades. Construction of Unique Buildings and Structures. 2 (17) (2014), pp [3] N. I. Vatin, D. V. Nemova: Increase of power efficiency of buildings of kindergartens. Construction of Unique Buildings and Structures. 3 (2012), pp [4] N. I. Vatin, A. S. Gorshkov, D. V. Nemova: Energy efficiency of envelopes at major repairs. Construction of Unique Buildings and Structures. 3 (8) (2013), pp [5] A. Dodoo, L. Gustavsson, R. Sathre, Primary energy implications of ventilation heat recovery in residential buildings, Energy and Buildings, Volume 43, Issue 7, (2011), pp [6] A. Kaklauskas, J. Rute,, E.K. Zavadskas, A. Daniunas, V. Pruskus, J. Bivainis, R. Gudauskas, V. Plakys: Passive House model for quantitative and qualitative analyses and its intelligent system. Energy and Buildings, 50, (2012), pp [7] I.F. Livchak, Yu.Ya Kuvshinov, Razvitiye teplosnabzheniya, klimatizatsii i ventilyatsii v Rossii za 100 poslednikh let: Uchebnoye posobiye, Moskva (2004) p. 132 [8] V. Murgul: Solar energy in the reconstruction of urban environment of historic building Saint-Petersburg, Architecture and Modern Information Technologies, 2 (23) (2013), pp [9] Y. Wang, Fu-Yun Zhao, J. Kuckelkorn, H. Spliethoff, E. Rank, School building energy performance and classroom air environment implemented with the heat recovery heat pump and displacement ventilation system, Applied Energy, Volume 114, ( 2014), pp [10] L. D. Boguslavskiy, V. I. Livchak, V. P. Titov, Energosberezheniye v sistemakh teplosnabzheniya, ventilyatsii i konditsionirovaniya vozdukha. Moskva. (1990) p. 154 [11] Tekhnicheskiye rekomendatsii po organizatsii vozdukhoobmena v kvartirakh zhilykh zdaniy, Moskva, (2012), p. 278 [12] V. Murgul: Features of energy efficient upgrade of historic buildings (illustrated with the example of Saint-Petersburg). Journal of Applied Engineering Science, Vol. 12 (1) (2014), pp 1-10 [13] D. Nemova, V. Murgul, A. Golik, E. Chizhov, V. Pukhkal, N. Vatin: Reconstruction of administrative buildings of the 70s: the possibility of energy modernization. Journal of Applied Engineering Science, Vol. 12 (1) (2014), pp [14] V. Murgul: Improvement of the energy efficient properties of the houses in the historical area of Saint-Petersburg, Architecton: Proceedings of Higher Education, 4 (40) (2012), pp [15] E. Aronova, G. Radovic, V. Murgul, N. Vatin: Solar Power Opportunities in Northern Cities (Case Study of Saint-Petersburg). Applied Mechanics and Materials. Vols (2014), pp [16] D. Vuksanovic, V. Murgul, N. Vatin, E. Aronova: Shadowing impact on amount of power generated by photovoltaic modules. Applied Mechanics and Materials. Vols (2014), pp [17] S. Golovina, V. Murgul: Solar energy systems in the architecture of historic cities. Bulletin of Civil Engineers. 5 (40) (2013), pp

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