Agronomy Research 11 (2), 487 494, 2013 Combined air condiioning for heaing rooms and improving of indoor climae V. Viljasoo 1,*, J. Zadin 1, H. Jüris 2 and T. Pomerans 1 1 Insiue of Technology, Esonian Universiy of Life Sciences, Kruzwaldi 56, EE51014 Taru, Esonia; * Correspondence: viljo.viljasoo@emu.ee 2 Company AIRMAKER GTR, Riia 181A, EE51014 Taru, Esonia Absrac. Geohermal equipmen consiss of inake air pipes, vacuum wards and underground connecing pipes, placed near o a villa. The hea exchange venilaion equipmen MENERGA 191191 used in venilaion sysems makes air inside he device circulae. This paened equipmen differs from he analogues of Germany, Japan, Unied Saes, ec. by he cooling exchange device. This device enables remarkable advanages in mouning and consrucion by decreasing he lengh, insallaion deph and number of air pipes, simplifying and reducing he mainenance and increasing he equipmen durabiliy. The geohermal equipmen is mean for creaing an environmen wih a consan emperaure of 4 ºC and adjusable relaive humidiy in warehouses and basemens. I is for improving an indoor climae in villas basemens, preheaing, and air condiioning based on air heaing as well. This equipmen is indispensable when preheaing greenhouses and cooling air in he ho season. The analysis of air climae parameers (emperaure ϑ k, relaive humidiy W s, dew poin ϑ p, absolue humidiy W a, velociy v, oxygen conen O 2, carbon dioxide conen CO 2, posiive ligh air ions n +, negaive ligh air ions n ) passing hrough he geohermal equipmen is presened in he aricle. Hea echnical daa (air specific hea capaciy, characerisics of hea and cold exchange processes) are presened. This aricle summarises he research resuls of indoor climae qualiies and presens daa abou energeic-economical efficiency of he geohermal equipmen (air specific hea and gross capaciies, reurn air flow specific hea and gross capaciies, he economic effec of pre-heaing he villa and he pos-heaing expenses were analysed). Key words: geohermal, equipmen, climae, environmen. INTRODUCTION Ground hea is a grea energy reposiory accumulaed in he ground, sone surfaces and waer. Uilisaion of geohermal energy decreases pressure on he environmen caused by energy producion, reducing he dangers of polluion and healh risks conneced wih operaing chemical-based energy sources. Usage of ground hea in venilaion and air heaing sysems has been praciced for abou 150 years. In he paens of he Unied Saes of America, Germany and Japan (US-5131887, DE-3414973, JP 58095156 ec.) soluions for accumulaing ground hea energy and for air filraion are described, essenial for air heaing sysems. A useful model EE00329 of an analogous soluion is regisered in Esonia under he names of Jüris, H. and Piiger, L, paen number 0104. The regisered geohermal equipmen is mean for pre-heaing he incoming air (cold season), for cooling (warm 487
season), for improving inernal climae parameers and i differs from is predecessors by he applicaion of a cold exchange device. The aim of he research was o analyse he climae parameers of he air passing hrough he assembly of he working geohermal equipmen, hea-echnical parameers of he equipmen's hea and cold exchange device and energy-economical daa of he device, in order o make a prognoses abou suiabiliy of he device for house heaing and esablishing an inernal climae. In order o aain he objecives he following asks have been compleed: 1) evaluaion of he climae parameers of he working device; 2) analysis of he hermal-echnical parameers of he working device; 3) defining and analysing he energy-economical daa of he device. OBJECT AND METHODS The research objec was geohermal equipmen buil ino a house (Fig. 1), he climae parameers of he air inpu device of which (1...3), hea exchange device (5, ground source), air oupu device (6...13) and cold exchange device (14...20) were measured by a real ime nework. For his purpose diagnosic equipmen DATA LOGGER ALMEMO 2690-8 wih measuring sensors was used. Inernal and exernal climae qualiies of he air acive in he geohermal hea exchange device were analysed on he basis of heir basic characerisics (air emperaure ϑ k, air relaive humidiy W s, dew poin ϑ p, air absolue humidiy W a, air movemen speed ν, oxygen level in he air O 2, carbon dioxide level in he air CO 2, posiively loaded ligh aeroions n +, negaively loaded ligh aeroions n ). Figure 1. Graph of objec wih geohermal equipmen and echnical daa: 1 air inpu pipe lid; 2 exernal air inpu pipe (Ø 250 6000 mm, 4 pieces); 3 decompression chamber lid; 4 decompression chamber (4400 1500 1900 mm) 2 ; 5 air pipes (Ø 162 7000 mm, 19 pieces); 6 decompression chamber (4400 1500 1800 mm) (Fig. 2), 7 air inpu nozzle; 8 air inpu pipe (Ø 250 mm); 9 hea exchanger Menerga 191101 (Fig. 3); 10 inernal air inpu; 11 processed air oupu; 12 chimney base; 13 pollued air pipe; 14 airing pipes (Ø 110 mm, 4 pieces); 15 perforaed pipe (Ø 160 mm); 16 exracing pipe (Ø 160 mm); 17 ligh weigh aggregae (LWA) FIBO (7000 5000 400 mm); 18 concree floor; 19 polyehylene film; 20 venilaor. 2 lengh, widh, heigh 488
In order o obain reliable measured values, in accordance wih experimen planning heory (Melnikov e al., 1980) probabiliy α = 0.95. To achieve he se-up reliabiliy emanaing from he echnical daa of equipmen, measuremen error of sensors ε = ± 0.4σ, where σ is he sandard deviaion of arihmeic mean. Funcioning abiliy of hea and cold exchange device of he geohermal equipmen was measured according o he following mehod: 1. In hermal-echnical parameers of he equipmen's hea exchange device i was considered ha he ground is 7 5 m large land erriory wih unlimied deph. Air pipes (19 pieces) are placed in wo rows, in chess posiions up o 1.95 m deep in he ground. In ligh aggregae zone are placed 4 venilaion pipes (Fig. 4). 2. Considering he grea hermal capaciy of he ground (soil) c p = 1,840 J (kg K) -1 (Incropera & DeWi, 1996) and unlimied deph, i can be considered as an unlimied hea reposiory. 3. The influence of diurnal emperaure frequen variaion is relaively irrelevan (Kabashnikov e al., 2002). 4. I is presumed (Kabashnikov e al., 2002) ha ground emperaure i 4 6 C all-he-year-round. 5. There is proper hermal isolaion under he floor of building socle/basemen floor. 6. According o diagnosis daa he medium emperaure in March 2010 in he air inpu area was 11 C. 7. The oal lengh of he hea exchange area of air pipes is 63 m and air capaciy 0.65 m 3. 8. Airflow average speed in air pipes was 0.12 m s -1. Figure 2. The decompression chamber. Figure 3. The hea exchanger Menerga 191101. Air volume and weigh of consumpion are calculaed using formulas (Viljasoo e al., 2005) Õ e v S n Õ v S n, (1, 2), ek where Õ e air volume of consumpion m 3 s -1 ; v air velociy in he air pipe m s -1 ; S cross-secional area of he air pipe m 2 ; n number of air pipes; Õ ek weigh air consumpion of air volume kg s -1 ; ρ densiy of mois air a normal condiions kg(m 3 ) -1 (ρ = 1,293 (Liiske, 2002)). 489
In hea exchange of cold air indifferen capaciy is calculaed by he formula Q k Õ ek c nõ Q, (3) 1 4 ka where Q k cold specific capaciance of air kw; Õ ek air weigh of consumpion kg s -1 ; c nõ mois air specific hea kj (kg K) -1, (c nõ = 1.01); ϑ 1 emperaure of he air in he exernal environmen K; ϑ 4 average air emperaure in he second chamber K; Q ka cold losses kw (average of 10%). In he hea exchange par aken from he ground of differen hea he number is calculaed by he formula q s S k, (4) s k where q s from he ground of specific consumpion of hea W; S s heaing surface m 2 ; k hermal efficiency of hrough W (m 2 K) -1, (k = 6); Δϑ k he average emperaure difference K. Figure 4. Placemen of he pipes in case of limied building base area. The average emperaure difference beween he hea exchanges is calculaed k mp 4 mk 1, 2,3lg mp mk 4 1 (5) where ϑ k average emperaure difference K; ϑ mp soil emperaure K; ϑ 4 - average emperaure in he second chamber K; ϑ mk average emperaure of he air pipes above he soil K; ϑ 1 average ambien emperaure K. 490
Geohermal equipmen performance o influence hygienic characerisics of unipolariy ions is deermined by (Tšiževski, 1989) n q n, (6) n where q n unipolariy facor of ligh ions; n + posiively loaded ligh air ions cm -3 ; n - minus-loaded ligh air ions cm 3. The relaive freshness of he air is calculaed by he formula (Viljasoo & Tomson, 2002) q V 100 100, (7) q õ where V he relaive freshness of he air %; q reaed wih air ions unipolariy facor in spaces; q õ he maximum value of unipolariy facor (q õ = 1.3) in indoor environmen. Considering he fac ha here are many differen mehods o calculae he hea amoun needed for heaing he house, and he calculaions resuls are somewha differen, he following conrol calculaions have hereby been conduced. In he firs case he hermal uni capaciy amoun needed for heaing he house was calculaed using he formula, Q q V (8) s o e 491 12 1 where Q s hermal uni capaciy necessary for heaing he house W; q o house specific hermal uni characerisic W (m 3 K) -1 (q o = 0.87 (Žabo e al., 1983)); V e house exernal cubaure m 3 (V e = 500); ϑ 12 air emperaure in he house K; ϑ 1 exernal air emperaure K(ϑ 1 = -15 C); η correcion facor depending on he qualiy of he house (η = 0.6 (Žabo e al., 1983)). RESULTS AND DISCUSSION Based on he diagnosis daa he working parameers of he hea exchange device calculaed according o he condiions saed in he research mehod are he following: considering air gravimeric uni expendiure he cold uni capaciy of he air passing hrough he hea exchange device air pipes is 202.6 717.7 W (Table 1) in case of air flow medium speed 0.12 m s -1. Thus he cold amoun of air passing hrough air pipes depends mainly on exernal air emperaure. In connecion wih he fac ha according o he daa presened in lieraure (Incropera & DeWi, 1996; Kabashnikov e al., 2002) he pipes are placed a he deph 2 6 m in order o ensure he environmen wih sufficien ground emperaure (4 6 C), in case of he objec (Fig. 2) he possible emperaure of he ground (clay-earh soil) surrounding he pipes placed a he deph of medium 1.4 m, is 4 C.
Table 1. Work parameers of he hea exchange device of he geohermal equipmen Dae, ime Equaions, condiions Uni Hea Air specific specific consumpion volume Õ q s, W e 1. Õe v S n m 3 s -1 0.0235 2. Õ v S n kg s -1 0.0304 ek 3. Qk Õek cnõ 1 4 Qka kw Q k, kw 3.1. if 1 = 11, ϑ 4 = 4.9 C 0.2026 27.03.10 3.2. if 1 = 15, 4 = 4.0 C 0.7177 27.03.10 4. qs S k k W Source daa Provided C 27.03.10 4.1. if ϑ k1 = 2.13 K 447.3 27.03.10 4.2. if ϑ k2 = 3.42 K 717.7 v = 0.12 m s -1 S 1 = 0,0103 m 2 ϑ mk = 2 C A he same ime i is possible o assume ha he emperaure of he ground surrounding pipes placed a saed deph is 4 C and even 5 C. According o he saed emperaure opions (ϑ mp = 4.0; 5.0 C) and he resuls of calculaions based on he diagnosis daa he average hermal uni consumpion acquired from he ground in he equipmen s hea exchange device is 447.3 717.7 W. In Table 1 we can see ha during period (27.03.10) he cold uni capaciy of exernal air passing hrough he hea exchange air pipes was 202.6 W. A even colder imes (-15 C) he cold uni capaciy of exernal air passing hrough he air pipes was on average 717.7 W and a he same dae he average hea uni expendiure aken from he ground was 717.7 W, which also exceeds somewha he exernal air cold uni capaciy. Based on received calculaions he funcioning of he hea exchange device can be considered saisfacory. Climae parameers (Table 2) of working geohermal equipmen were diagnosed in rooms wih processed air, accordingly and hese were he following resuls: emperaures accordingly 22.27 and 20.51 C, relaive humidiy 56.5 and 52.66%, air flow speed 0.12 and 0.13 m s -1, air oxygen conen 20.07 and 20.17%; air carbon dioxide conen 0.05 and 0.08%. The saniary-hygienic condiions of he room can be judged and improved by defining and improving is elecrosaic condiion. The measuring resuls showed ha in he room wih processed air he uni quaniy of negaively loaded ligh air ions (5,286 and 4,002 cm -3 ). The amouns of posiively loaded ligh air ions were accordingly 5,103 and 3,195 cm -3. Thus in he room wih processed air he air and room saniary-hygienic condiion was very good (q = 0.97 and 0.80) from he poin of view of elecro climae. To sum up, he climae parameers in he room wih processed air were somewha beer han in he room wih unprocessed air, which is characerised by an increase of 25.38 and 38.46% in relaive air freshness in reference o he highes value of esablished norm (q = 1.3). 492
Table 2. Climaic characerisics of he geohermal equipmen N o Characeri Exernal Decompression Cellar Living Uni sic climae chamber room room Bedroom 1. ϑ ºC 11.10 4.88 18.86 22.27 20.51 2. W s % 71.90 93.30 55.60 56.5 52.66 3. ϑ p ºC 5.80 4.90 7.33 9.4 7.85 4. W a g kg -1 6.12 3.80 9.56 13.2 10.50 5. v m s -1 0.30 0.12 0.14 0.12 0.13 6. O 2 % 20.17 20.72 19.87 20.07 20.17 7. CO 2 % 0.08 0.12 0.10 0.05 0.08 8. n + cm -3 1,346 1,990 4,413 5,103 3,195 9. n cm -3 2,298 2,412 5,318 5,286 4,002 10. Σn ± cm -3 3,644 4,402 9,731 10,389 7,197 11. q 0.59 0.83 0.83 0.97 0.80 12. S % 54.62 36.15 36.15 25.38 38.46 The uni hermal capaciy (Formula 8 (Žabo e al., 1983)) needed for heaing he house is 9.4 kw and he oal hermal capaciy during he heaing period (5,040 h) is 47.35 MWh. The oal hermal capaciy needed for heaing he house during he heaing period is 40.8 MWh, based on lieraure sources (Liiske, 2002). In connecion ha geohermal equipmen was in winer condiions (exernal air emperaure 15 C) he air hermal uni capaciy acquired wih he help of geohermal equipmen (Menerga 191101 only in venilaion mode) would be a emperaure 15...4 C 4.96 kw and air oal hermal capaciy during he heaing period would be 24.99 MWh. For aferheaing he house from emperaure 4 21 C wih a hermal exchange elecrocalorifier he received uni hermal capaciy is 4.44 kw and air oal hermal capaciy during he heaing period 22.36 MWh. The reurned hea uni hermal capaciy from emperaure 24 21 C is 0.78 kw and oal capaciy during he heaing period 3.95 MWh. The ground hea and he reurned hea added uni capaciy is 5.74 kw and oal capaciy during he heaing period is 28.93 MWh. The average oal hermal capaciy needed for heaing he building is 47.35 MWh. The ground hea and he reurned hea oal capaciy (28.93 MWh) during he heaing period represen approximaely 61.1% of his. CONCLUSIONS 1. The funcioning of cold and hea exchange devices of a working geohermal equipmen wih he cold exchange device may be considered saisfacory in condiions of saed air flow speed. 2. Climae parameers and he saniary-hygienic condiions are comparaively beer in he rooms (25.38 38.46%) wih processed air. 3. The cold uni capaciy of exernal air passing hrough he hea exchange air pipes was on average 717.7 W. 4. The average hea uni expendiure aken from he ground was 717.7 W. 5. Theoreically he uni hermal capaciy achieved wih help of geohermal equipmen would be 0.717 kw and oal hermal capaciy during he heaing period 3.62 MWh. 493
REFERENCES Incropera, F.P. & DeWi, D.P. 1996. Fundamenals of Hea and Mass Transfer IV Ediion. John Wiley & Sons, New York, 886 pp. Kabashnikov, V.P., Danilevskii, L.N., Nekrasov, V.P., Viyaz, I.P. 2002. Analyical and numerical invesigaion of he characerisics of a soil hea exchanger for venilaion sysems. Inernaional Journal of Hea and Mass Transfer. 45, 2407 2418. Liiske, M. 2002. Sisekliima. Taru, 188 pp. (in Esonian). Melnikov, S.V., Aleshkin, V.R., Roshchin, P.М. 1980. Experimens planning in sudies of agriculural processes. Kolos, 168 pp. (in Russian). Žabo, V. Lebedev, D. Moroz, V. 1983. Handbook of hea supply of agriculural enerprises. Moscow, 320 pp. (in Russian). Tšiževski, A.L. 1989. Air ionizaion in he naional economy: Second ediion. Sroyizda, Moscow, 488 pp. (in Russian). Viljasoo, V., Tomson, I. 2002. Maerials indoor climae properies in animal farm. Agraareadus: Journal of Agriculural Science. 2, pp. 114 126. (in Esonian). Viljasoo, V., Treial, J., Tomson, I. 2005. Geohermal device wih cold exchaning uni for rooms heaing and he indoor climae improving. Agraareadus: Journal of Agriculural Science. 15(3), 181 190. (in Esonian, English absr.). Viljasoo, V., Treial, J., Tomson, I. 2005. Geohermal device wih cold exchaning uni for rooms heaing and he indoor climae improving. Inernaional Scienific Conference. Advanced echnologies for energy produccing and efecive uilizaion, Jelgava, Lavia, pp. 47 52. Viljasoo, V., Treial, J., Tomson, I. 2005. The efficiency of geohermal equipmen wih cool exchange device. Ecological Energy Resources in Agriculure. Proceedings of he 9h Inernaional Conference, Lihuanian Universiy of Agriculure, Raudondvaris, Lihuanian, pp. 145 152. 494