Agronomy Research 13(1), 245 252, 2015 Heatng and ventlaton n mlkng parlours J. Papez * and P. Kc Czech Unversty of Lfe Scences Prague, Faculty of Engneerng, Kamycka 129, 16521 Prague 6, Czech Republc; * Correspondence: papez@tf.czu.cz Abstract. The am of ths paper s to show the results of the measurement of man mcroclmatc parameters (temperature and relatve humdty) n mlkng parlours and compare the obtaned results wth values recommended n relevant standards. Temperature and relatve humdty can affect anmal welfare as well as the well-beng of workers. These parameters were measured n three rotary mlkng parlours wth herrngbone type of stalls, each for 24 dary cows. Two of these mlkng parlours were bult n 2001 and one was bult n 2009. Measurements were taken durng the wnter and summer perods, under extremely cold or hgh temperature condtons. Measurements were taken durng the mlkng process for about two hours usng sutable sensors for measurement of ndoor temperature and relatve humdty. The data of outsde temperature and relatve humdty were also obtaned and compared wth ndoor data. The fnal results of the research were generalzed. It s obvous from the results of measurements of selected mlkng parlours that heatng and ventlaton of mlkng parlours s nsuffcent. To set up adequate heatng power, the heat balance of mlkng parlours was calculated. For adequate ventlaton, the necessary flow of fresh ar was calculated for both wnter and summer perods. Also the methods of how to acheve these ar flows are presented. Key words: measurement, relatve humdty, temperature, THI. INTRODUCTION The am of ths artcle s to show the results of measurement of man mcroclmatc parameters (temperature and relatve humdty) n mlkng parlours and to compare the obtaned results wth the values recommended n relevant standards. Envronmental condtons are determned by characterstc factors, especally by physcal factors, chemcal factors and bologcal factors. Thermal condton of the ndoor envronment s characterzed by thermal and humdty varables whch affect the resultng mental and physcal state of an anmal or person n agrcultural buldngs. The result of the analyss of thermal envronment s the formaton of optmal condtons for human and anmal organsms. Requred optmal temperature n mlkng parlour n the wnter perod s 14 16 C (mnmum 10 C). In the summer perod, the requred optmal temperature should be n the range of 14 22 C (maxmum 26 C). (Novy et al., 2006; Choupek & Suchy, 2008; Koznarova & Klabzuba, 2008; Zejdova et al., 2014) Thermal condton of the ndoor envronment s also nfluenced by relatve humdty. Hgh water vapour content n the ar reduces the possblty of coolng the body of a man or an anmal by evaporaton. It can cause heat stress already at a relatvely low temperature of ndoor envronment. Relatve humdty should by deally n the range of 40 80%. The maxmum allowable value of relatve humdty accordng to Czech 245
standard CSN 73 0543 2 s 85%. Wet ar s a good conductor of heat. Long-term exposure of relatve humdty above 85% adversely affects the organsm and apparatus and could damage wooden elements of the buldngs. (Kc & Broz, 1995; Kunc et al., 2007; Pavelek & Stetna, 2007; Papez & Kc, 2013; Zejdova et al., 2014) The effect of combnatons of temperature and humdty s ncluded n the temperature humdty ndex (THI). Ths ndex s wdely used to descrbe the heat stress and t s also a good ndcator of stress temperature envronment condtons. THI value below 70 s consdered comfortable for cattle. THI n the range of 70 78 s consdered stressful and values hgher than 78 cause extreme sufferng (the organsm s unable to mantan the thermoregulatory mechansms, or normal body temperature). (Armstrong, 1994; Zejdova et al., 2014) MATERIALS AND METHODS The basc assumpton of ths research s to perform measurements of man mcroclmatc parameters (temperature and relatve humdty) n mlkng parlours and to compare obtaned results wth values recommended n relevant standards. The am of ths paper s also to fnd and defne the methods for the mprovement of ndoor condtons n mlkng parlours n case of exceedng (or not reachng) allowable lmts (settng up adequate heatng power and necessary flow of fresh ar). To avod bg dfferences between the mlkng parlours from the pont of vew of other mcroclmatc parameters, the thermal comfort n the space was contnuously measured by globe temperature (measured by globe thermometer FPA 805 GTS wth operatve range from 50 to +200 C wth accuracy ± 0.01 K and dameter of 0.15 m) together wth temperature and humdty of surroundng ar measured by sensor FH A646 21 ncludng temperature sensor NTC type N wth operatve range from 30 to +100 C wth accuracy ± 0.01 K, and ar humdty by capactve sensor wth operatve range from 5 to 98% wth accuracy ± 0.1%. All data were measured contnuously and stored at ntervals of three mnutes to measurng nstrument ALMEMO 2590 9 durng the measurement (approxmately 120 mnutes). Three mlkng parlours were measured durng the wnter and summer perods, under extremely cold or hgh temperature condtons. The measurement durng the mlkng process lasted for about two hours. The data of outsde temperature and relatve humdty were also obtaned and compared wth ndoor data. The results of measurements were processed by Excel software and verfed by statstcal software Statstca 12 (t test, ANOVA and TUKEY HSD Test) All three measured mlkng parlours are rotary wth herrngbone type of stalls, each for 24 dary cows. Two of these mlkng parlours were bult n 2001 and one was bult n 2009. The dfferences are n heatng and ventlaton system. Mlkng parlour A There s only natural ventlaton n ths mlkng parlour through the wndows wth a total area of about 14 m 2 and two skylghts, each of sze 2 x 2 m. Ths mlkng parlour s heated through four radant heatng panels wth a total output of 9.6 kw. 246
Mlkng parlour B Forced (over pressure) ventlaton wth a flow rate 3,240 m 3 h 1 s nstalled n ths mlkng parlour. Ths system s equpped wth an nlet ar heater wth power of 24 kw. Mlkng parlour C There s only natural ventlaton n ths mlkng parlour through the wndows wth an area of 6.48 m 2 and four ventlaton chmneys; each of sze 0.3 x 0.3 m. Ths mlkng parlour s heated through two radant heatng panels wth a total output of 8 kw. Theory and modellng Thermal condton of the ndoor envronment can be controlled by operatonal temperature and relatve humdty. The operatonal temperature s defned as a unform temperature of enclosed space, black n terms of radaton, n whch the heat shared by convecton and radaton would be the same as n the real thermally unbalanced envronment (Kabele & Veverkova, 2003). Accordng to Novy (Novy et al., 2006) the operatonal temperature s determned by the followng equaton: t o é 0,25 ù ê æ ö ç t - 4 7 tg ú = A t + ( 1- ) 4 A ê ( tg + 273) + 1.855 10 1.4 ( tg - t ) - 273, ç D ú (1) ê è ø ú ë û where: t o operatonal temperature ( C); A coeffcent of velocty (for ar velocty up to 0.2 m s 1, A = 0.5); t nternal temperature of ar ( C); t g temperature measured by globe thermometer ( C); D dameter of globe thermometer (m). Relatve humdty s obtaned drectly by measurng. Effect of combnatons of temperature and relatve humdty s ncluded n the THI. Ths ndex s wdely used to descrbe the heat stress and t s also a good ndcator of stress temperature envronment condtons. Accordng to Zejdova (Zejdova et al., 2014), the THI s determned by the followng equaton: ( t -14.4) RH THI = 0.8 t + + 46.4, (2) 100 where: THI temperature-humdty ndex ( ); t nternal temperature of ar ( C); RH nternal relatve humdty of ar (%). The average values, ncludng standard devaton, were calculated from the results of measurements for each of the mcroclmatc parameters (operatonal temperature and relatve humdty) and THI. RESULTS AND DISCUSSION The man objectve of ths artcle s to show the results of the measurement of man mcroclmatc parameters (temperature and relatve humdty) n mlkng parlours and to compare obtaned results wth values recommended n relevant standards. 247
Summer perod The results of the measurement of man mcroclmatc parameters and THI n the summer perod are shown n Table 1. Table 1. Average values and standard devaton of operatonal temperature (t o), relatve humdty (RH ) and THI n mlkng parlours A C n the summer perod, ncludng external temperature (t e) and relatve humdty (RH e) Parlour t o ( C) RH (%) THI ( ) t e ( C) RH e (%) A 28.81 ± 0.37 55.3 ± 3.2 76.40 ± 0.73 a 28.86 52.7 B 28.88 ± 1.27 57.9 ± 3.0 76.81 ± 1.05 a 29.57 54.8 C 20.20 ± 0.60 51.1 ± 4.5 65.05 ± 0.88 b 18.53 41.4 *The results that exceed allowable lmts are hghlghted n bold. **Dfferent letters (a, b) n the superscrpt refer to statstcally sgnfcant dfference at level P = 0.05 (ANOVA and TUKEY HSD Test). The operatonal temperature n mlkng parlour A s correspondng wth external temperature (t test, P = 0.83) as well as the operatonal temperature n mlkng parlour B (t test, P = 0.19). The maxmum allowable temperature (26 C) was exceeded n both of these mlkng parlours. The operatonal temperature n the mlkng parlour C s n the optmum range (14 22 C) thanks to low external clmatc condton durng the measured perod. Accordng to the statstcal evaluaton (t test, P < 0.05) the ndoor operatonal temperature n mlkng parlour C does not correspond wth external temperature. Internal relatve humdty was hgher than external relatve humdty n all three mlkng parlours (t test, P < 0.05), however, stll below allowable maxmum of 85%. THI values ndcate stress condton for dary cows (because of hgh external temperature) n mlkng parlours A and B and they could be consdered as equal (TUKEY HSD Test, P = 0.25). Improvng of the nternal condtons could be ensured by the nstallaton of overpressure forced ventlaton, whch ncreases ar velocty (Kc & Gurdl, 1999). Accordng to Czech standard CSN 73 0543 2, the requred mass flow rate of fresh ar for heat removal n the summer perod for cows s determned by the followng equaton: 0,74 v ma x = 0.95 y z Z mz M &, 10, (3) where: M & v, max requred mass flow rate of fresh ar (kg s 1 ); y coeffcent, weght of the constructon; z coeffcent, area of translucent structures; Z average number of cows n mlkng parlour; m z average weght of one cow (kg). Accordng to equaton (3) t s necessary to ensure mass flow of fresh ar for mlkng parlours for 24 dary cows n range of 3.43 3.91 kg s 1 (correspondng volume flow 10,284 11,732 m 3 h 1 ), dependng on y and z. Wnter perod The results of measurement of man mcroclmatc parameters and THI n wnter perod are shown n Table 2. -3 248
Table 2. Average values and standard devaton of operatonal temperature (t o), relatve humdty (RH ) and THI n mlkng parlours A C n the wnter perod, ncludng external temperature (t e) and relatve humdty (RH e) Parlour t o ( C) RH (%) THI ( ) t e ( C) RH e (%) A 12.07 ± 1.60 a 68.9 ± 3.2 a 51.58 ± 1.71 a 1.07 79.46 B 11.82 ± 0.86 a 94.0 ± 1.2 b 52.26 ± 1.03 a,b 2.38 87.46 C 12.26 ± 1.03 a 89.2 ± 2.8 c 53.19 ± 1.65 b 1.33 94.00 *The results that exceed (or do not reach) allowable lmts are hghlghted n bold. **Dfferent letters (a, b, c) n the superscrpt refer to statstcally sgnfcant dfference at level P = 0.05 (ANOVA and TUKEY HSD Test) The operatonal temperature s below the optmum range of 14 16 C n all three mlkng parlours (t test, P < 0.05). It s also possble to consder the operatonal temperature n all three mlkng parlours as equal (ANOVA, P = 0.31). Internal relatve humdty exceeds allowable lmt of 85% n mlkng parlours B and C (t test, P < 0.05). In mlkng parlour A, the relatve humdty s below allowable lmt of 85% (t test, P > 0.05). THI values do not ndcate stress condton for dary cows n the wnter perod. Hgher relatve humdty n the mlkng parlour s probably caused by nadequate ventlaton n the mlkng parlour. The Czech standard CSN 73 0543 2 calculates the requred mass flow rate of fresh ar n the wnter perod separately for exhaust of water vapour and separately for exhaust of CO 2. Accordng to Czech standard CSN 73 0543 2, the mass flow rate of fresh ar for exhaust of water vapour s determned by the followng equaton: -3 & Z mdo+dmdo) 10 vd =, (4) Dxe M ( & & where: M & vd mass flow rate of fresh ar for exhaust of water vapour (kg s 1 ); m& do total producton of water vapour (mg s 1 pcs 1 ) D m& do ncreased evaporaton for underfloor heatng (mg s 1 pcs 1 ); D xe dfference of specfc humdty of nternal -1 and external ar ( g kg d.a. ) Accordng to Czech standard CSN 73 0543 2, the mass flow rate of fresh ar for exhaust of CO 2 s determned by the followng equaton: M& vu = Z m& u K - K u ue r, (5) where: M & vu mass flow rate of fresh ar for exhaust of CO 2 (kg s 1 ); m& u CO 2 producton of 1 dary cow (mg s 1 ); K u desgn value of the concentraton of CO 2 n the nternal ar (mg m 3 ); K ue desgn value of the concentraton of CO 2 n the external ar (mg m 3 ); ρ nternal ar densty (kg m 3 ). 249
The requred mass flow rate of fresh ar n the wnter perod s determned by the followng equaton: M & = max( M& ; M& ), (6) v vd Accordng to equatons (4) to (6), t s necessary to ensure n mlkng parlour A the mass flow rate 0.79 kg s 1 (volume flow rate 2,375 m 3 h 1 ), n mlkng parlour B 0.81 kg s 1 (volume flow rate 2,439 m 3 h 1 ) and n mlkng parlour C 0.89 kg s 1 (volume flow rate 2,696 m 3 h 1 ). It s possble to acheve these mass flows by natural ventlaton. Accordng to varous authors (Chysky et al., 1993; Novy et al., 2006) the calculaton of requred buoyancy for natural ventlaton s determned by the followng equaton: vu D p=dp +Dp = g ( r -r ) h, (7) o e where: Δp total pressure dfference (effectve buoyancy) (Pa); Δp the pressure requred to overcome the resstance n nlet openngs (Pa); Δp o the pressure requred to overcome the resstance n outlet openngs (Pa); g gravtatonal constant (m s 2 ); ρ e external ar densty (kg m 3 ); ρ nternal ar densty (kg m 3 ); h heght dfference of axes of nlet and outlet openngs (m) In practce, the effectve buoyancy s dvded to the pressures requred to overcome the resstance n nlet and outlet openngs n the rato 1:1. The requred areas of nlet and outlet openngs are determned by the followng equatons (Chysky et al., 1993; Novy et al., 2006): S S o M& v = m 2 r Dp M& v = m 2 r Dp o e o, (8), (9) where: S requred area of nlet openngs (m 2 ); S o requred area of outlet openngs (m 2 ); μ a μ o coeffcents of flows n nlet and outlet openngs. An overvew of requred and nstalled nlet and outlet openngs accordng to the equatons (7) to (9) s shown n Table 3. Table 3. Overvew of requred and nstalled nlet and outlet openngs for natural ventlaton n mlkng parlours A C n the wnter perod Parlour Requred S (m 2 ) Requred S o (m 2 ) Installed S (m 2 ) Installed S o (m 2 ) A 1.39 0.97 14.00 8.00 B 0.84 2.23 0.00 0.00 C 2.41 1.16 6.48 0.36 * Inadequate areas of nlet and outlet openngs are hghlghted n bold. 250
Adequate nlet and outlet openngs are nstalled only n mlkng parlour A, so there s no problem wth relatve humdty. Other mlkng parlours have nadequate nlet and/or outlet openngs and n these mlkng parlours the measured relatve humdty was hgher than allowed. To fx the problem wth relatve humdty n these mlkng parlours, t s necessary to make adequate nlet and outlet openngs (or usng forced ventlaton nstalled n parlour B). The lower temperature than the optmum durng the measurement ndcates nadequate heatng n mlkng parlours. To set up adequate heatng power, t s necessary to count the heat balance of a mlkng parlour (Kc et al., 2007; Zajcek & Kc, 2014). Accordng to Czech standard CSN 73 0543 2, the heat balance s determned by followng equaton: where: power (W); Q & Q& - Q& - Q& = 0 (10) c + t v p Q & c apparent producton of sensble heat (W); Q & v ventlaton heat loss (W); Q & p buldng s heat loss (W). Q & t adequate heatng Adequate heatng power calculated accordng the equaton (10) together wth nstalled heatng power s shown n Table 4. Table 4. Adequate and nstalled heatng power and adequate heatng power usng heat recovery system wth 50% effcency n mlkng parlours A C n the wnter perod Parlour Adequate Q & Installed t Q & Adequate t Q & usng heat recovery t (W) (W) system wth 50% effcency (W) A 11,246 9,600 748 B 9,954 24,000 2,317 C 8,931 8,000 4,704 * Inadequate heatng power s hghlghted n bold. Accordng to the equaton (10) and results n Table 4, t s obvous that heatng power n mlkng parlour A and C s nadequate (the heatng power n mlkng parlour B s adequate, but not used). The problem wth heatng power could be solved usng forced ventlaton wth heat recovery system. When usng forced ventlaton wth heat recovery system wth 50% effcency, the heatng power calculated accordng to equaton (10) s more than suffcent (see table 4). CONCLUSIONS The results of measurement show that the ndoor envronment of mlkng parlours s nfluenced by thermal condton (operatonal temperature and relatve humdty). From the results of measurements of selected mlkng parlours t s obvous that heatng and ventlaton s nsuffcent. In the summer perod, the operatonal temperature n the mlkng parlour corresponds to external temperature n days wth hgh external temperature (around 30 C). Internal relatve humdty s below the crtcal lmt of 85%; however, t s hgher 251
than external relatve humdty. Accordng to THI, combnaton of hgh temperature and relatve humdty s stressful for dary cows. Improvng of the nternal condtons could be ensured by nstallaton of overpressure forced ventlaton, whch ncreases the ar velocty n the mlkng parlour. The mlkng parlour for 24 dary cows constructed from lght-weght materal (mlkng parlour B) needs a flow of fresh ar wth the volume of about 12,000 m 3 h 1. The mlkng parlours constructed from medum-weght materal (mlkng parlours A and C) need a flow of fresh ar wth the volume of about 10,500 m 3 h -1. Internal relatve humdty over 85% ndcates nadequate ventlaton. In the wnter perod, natural ventlaton s suffcent. Natural ventlaton requres adequate nlet and outlet openngs. Problem of low operatonal temperature s caused by nadequate nstalled heatng power. One of the optons for solvng ths problem s to ncrease the heatng power by nstallaton of addtonal radant heatng panels. Another soluton can be usng forced ventlaton wth heat recovery system nstead of natural ventlaton. ACKNOWLEDGEMENTS. Supported by Internal grant agency of Faculty of Engneerng, Czech Unversty of Lfe Scences n Prague no: 2015:31170/1312/3114. REFERENCES Armstrong, D.V. 1994. Heat stress nteracton wth shade and coolng. Journal of Dary scence 77, 2044 2050. CSN 73 0543 2. 1998. Internal envronment n buldngs for anmals. Part 2: Ventlaton and heatng. CNI, Praha, 36 pp. (n Czech) Chloupek, J. & Suchy, P. 2008. Mcroclmatc measurements n anmal houses. VFU, Brno, 229 pp. (n Czech) Chysky, J., Hemzal, K., Drkal, F., Kubcek, L. & Novy, R. 1993. Ventlaton and Ar Condtonng. BOLIT, Brno, 560 pp. (n Czech) Kabele, K & Veverkova, Z. 2003. Modellng of operatonal temperature. Heatng Ventlaton Installaton. 12, 33 37. (n Czech) Kc, P. & Broz, V. 1995. Creaton of Stable Envronment. IVV MZe CR, Praha, 47 pp. (n Czech) Kc, P. & Gurdl, GAK. 1999. Trends n ventlaton and ar condtonng of anmal houses. Conference Proceedngs - Internatonal Conference on Trends n Agrcultural Engneerng. CZU, Praha, CZ, pp. 389 393 Kc, P., Kalvoda, T., & Zavadl, V. 2007. Energy savngs by heat recovery n ventlaton. Conference Proceedngs - 3rd Internatonal Conference on Trends n Agrcultural Engneerng. CZU, Praha, CZ, pp. 215 218 Koznarova, V. & Klabzuba, J. 2008. Mcroclmate of Stables. CZU, Praha, 29 pp. (n Czech) Kunc, P., Knzkova, I., Prkryl, M., Maloun, J. & Novak, P. 2007. Techncal, Anmalstc and Humane Aspects of Mlkng. CZU, Praha, 60 pp. (n Czech) Novy, R., Broz, K., Drkal, F., Hemzal, J. & Hemerka, J. 2006. Envronmental Engneerng. CVUT, Praha, 267 pp. (n Czech) Papez, J. & Kc, P. 2013. Wood Mosture of Rural Tmber Constructons. Agronomy Research 11, 505 512. Pavelek, M. & Stetna, J. 2007. Expermental Methods n Envronmental Engneerng. CERM, Brno, 215 pp. (n Czech) Zejdova, P., Chladek, G. & Falta, D. 2014. Influence of stable envronment on behavour and mlk producton of dary cows. Mendel Unversty, Brno, 26 pp. (n Czech) Zajcek, M. & Kc, P. 2014. Heatng of large agrcultural and ndustral buldngs. Agronomy Research 12, 237 244. 252