Thermography in Civil Engineering for Buildings Assessment - Detection of Different Kinds of Defects

Infracrvena termografija je metoda beskontaktnog mjerenja temperature i njezine raspodjele na površini promatranog objekta. Primjena termografije u zgradarstvu pruža velike mogućnosti kontrole kvalitete izvedbe kod novih građevina, ali i procjene trenutnog stanja starijih objekata. Osim što daje uvid u stanje objekta u smislu toplinske izolacije objekta, infracrvena termografija se može uspješno primijeniti za ocjenu stanja ovojnice građevine: otkrivanja različitih tipova grješaka (nedostataka i oštećenja) - otkrivanje mjesta odvajanja žbuke od podloge i mogućeg prisustva zraka ili vlage u slojevima ispod vanjske žbuke, te za procjenu stanja ravnih krovova - otkrivanje mjesta odvajanja sloja krovne ljepenke od podloge. Premda postoje različiti ograničavajući čimbenici kod termografskog snimanja građevinskih objekata, termografija se afirmirala kao metoda toplinske kontrole bez razaranja koja, u odnosu na neke druge metode nerazornog ispitivanja, posjeduje čitav niz prednosti. Između ostalog, metodom je omogućena trenutna analiza objekta na mjestu mjerenja kao i kontrola relativno velikih površina u kratkom vremenu, a naknadnom analizom moguća je i relativno jednostavna procjena kvalitete toplinske izolacije/toplinskih gubitaka objekta te otkrivanje strukture objekta ispod sloja žbuke. U radu su obrađeni primjeri detekcije različitih grešaka u području zgradarstva s osvrtom na zahtjeve norme HRN EN 13187. Obrađeni su slučajevi različitih stupnjeva oštećenja ovojnice zgrade, prisustvo vlage u zidovima objekta, toplinski mostovi i nekvalitetno brtvljenje, te prisustvo vlage i zraka u strukturi ravnog krova. U radu je posebno obrađeno mjerenje provedeno na upravnoj zgradi tvrtke Jadrolinija Rijeka, čiji je cilj bio utvrđivanje trenutnog stanja fasade i sukladno tomu davanje procjene o potrebi njezine sanacije. Za taj je slučaj, u sklopu analize termograma, provedena i numerička analiza prijenosa topline za karakteristične dijelove fasade sa i bez grešaka te su rezultati uspoređeni s rezultatima mjerenja.Infrared thermography is a method of contact-free temperature measurement providing temperature distribution on the surface of the observed building. The use of thermography in civil engineering for building assessment purposes opens up large possibilities for control of construction quality when newly built edifices are concerned, but also when estimation of the current state of the old buildings is needed. Besides giving insight into the state of the building insulation quality, infrared thermography can be successfully applied in the evaluation of the building envelope: for detecting different defect types (flaws and damage) – for detecting locations where the plaster layer is detached from the wall base with possible presence of air or moisture in the layers beneath the outer plaster, as well as for estimation of the state of the plain roofs - detecting locations where the roof cardboard is detached from the base. Although there are different limitations when thermography inspection of buildings is concerned, infrared thermography is recognized as a thermal non-destructive testing method, which holds many advantages with respect to the other methods of non-destructive testing. Among others, the method enables instant analysis of the building at the location of the measurement, as well as the control of relatively large surfaces in a short period of time. In addition, post-analysis enables a relatively straight forward estimation of thermal insulation quality, of the building’s heat losses as well as estimation of the structure beneath the plaster layer of the building. This paper gives the examples of the detection of different defect types appearing in building structures along with an overview of the requirements of Croatian norm HRN EN 13187. Cases of different degrees of damage present in the building envelope are analyzed, as well as the presence of the moisture in building walls, the existence of thermal bridges and inadequate tightening, the presence of moisture and air in the structure of plain roofs. The measurements presented in this work were performed on the headquarter building of the company Jadrolinija Rijeka. The goal of this measurement was to determine the current state of the building facade and to give estimation of the extent of the facade recovery needed. For this purpose, together with the detailed thermogram analysis, the numerical analysis of the heat transfer through the characteristic facade parts with and without defects present in the structure was performed and numerical results were compared to the ones obtained by measurement

Rad broda u nisko-temperaturnom okruženju

U članku se razmatra projektna i operativna problematika svojstvena plovilima namijenjenim službovanju u nisko-temperaturnom okruženju. Pri tom se naglasak stavlja na određivanje termalnih odziva broda sa svrhom pravilnog izbora konstrukcijskih materijala trupa i opreme izloženih niskotemperaturnim utjecajima, kao i kapaciteta brodskoga toplinskog postrojenja. Radi vjerodostojnoga simuliranja temperaturnih odziva strukture, te neustaljenih toplinskih opterećenja karakterističnih, mikroklimatski, defi niranih brodskih prostora u realističnom okruženju, objašnjava se i primjerima ilustrira primjena koncepta toplinskih mreža u modeliranju nastupajućih toplinskih interakcija. S tim u vezi, dan je pristup modeliranju karakterističnih okolišnih veličina koje su u interakciji s brodom, kao i pristup modeliranju toplinskih fenomena tijekom promjene agregatnoga stanja toplinskim interakcijama obuhvaćenih medija

A SOLUTION TO STEFAN PROBLEM USING EULERIAN TWO FLUID VOF MODEL

A novel approach for the solution of Stefan problem within the framework of the multi fluid model supplemented with Volume of Fluid (VOF) method, i.e. two-fluid VOF, is presented in this paper. The governing equation set is comprised of mass, momentum and energy conservation equations, written on a per phase basis and supplemented with closure models via the source terms. In our method, the heat and mass transfer is calculated from the heat transfer coefficient, which has a fictitious function and depends on the local cell size and the thermal conductivity, and the implementation is straightforward because of the usage of the local value instead of a global parameter. The interface sharpness is ensured by the application of the geometrical reconstruction scheme implemented in VOF. The model is verified for three types of computational meshes including triangular cells, and good agreement was obtained for the interface position and the temperature field. Although the developed method was validated only for Stefan problem, the application of the method to engineering problems is considered to be straightforward since it is implemented to a commercial CFD code only using a local value; especially in the field of naval hydrodynamics wherein the reduction of ship resistance using boiling flow can be computed efficiently since the method handles phase change processes using low resolution meshes

Infrared Thermography as a Prediction Tool for the Irrigation Requirement in Agriculture

This paper deals with the possibility of using infrared thermography to determine the irrigation requirement for a given field depending on the water stress level of the plants. The experiments were performed on vines at the site in the village of Jadrtovac near Šibenik, Croatia. The water stress level of plants was determined through leaf temperature measurements and measurements of leaf water potential (LWP). Leaf temperature measurements were performed using infrared thermography. Based on these measurements the relationship between the LWP and a derived factor, Crop Water Stress Index (CWSI) was investigated. The results obtained show that infrared thermography could be successfully used to measure the leaf temperature, which is the input parameter for calculating the CWSI

Low-Temperature Ship Operations

The article considers the design and operational problems inherent to vessels intended for operation in low-temperature environment. In doing so, emphasis is placed on the determination of ship’s thermal responses for the purpose of proper selection of the construction materials of the hull and the equipment that are exposed to low temperature effects, and the heat capacity of the ship’s thermal plant. In order to simulate in a reliable way the temperature response of relevant structures and unsteady heating loads of the typical ship spaces having a defi ned own microclimate in a realistic environment, the application of the concept of thermal networks in the modelling of thermal interactions is explained and is illustrated with examples. In this regard, an approach to the modelling of environmental items interacting with the ship, and to the modelling of thermal phenomena during the change of the aggregate state of the media involved by the acting thermal interactions is given

Utjecaj hormonskog statusa na termografski nalaz kod raka dojke

The aim of this study was to investigate the association of infrared imaging findings and hormone receptor (estrogen and progesterone) status in breast cancers. The study was carried out at Department of Surgical Oncology and Department of Pathology, Sestre milosrdnice University Hospital Center, in collaboration with licensed infrared thermography experts. The study involved 75 female patients with invasive breast tumors. Thermography findings were compared with different immunohistochemical findings (hormone status positive or negative). Seventy-five female patients aged 36 to 86 years, mean age 64±11.36 years, were examined. The tumor itself and the breast containing the tumor were statistically significantly warmer (p<0.001) than the healthy breast in all study patients. There was no statistically significant difference (p>0.05) between patients with positive and those with negative estrogen receptors. Unlike all previously published results of various thermographic studies, results obtained in this study on the hormone receptor status analyzed and its impact on thermographic findings indicated that estrogen negative tumors had a higher maximum and average temperature than estrogen positive tumors. It was also observed that estrogen negative tumors had lower impact on warming of the entire breast, and that maximum and average temperature of the affected breast was higher in estrogen positive tumors. Arithmetic means of maximum and average tumor temperatures were statistically significantly higher for progesterone negative tumors compared with progesterone positive tumors (p<0.05). Thermographic findings correlated with the specific hormonal status of breast invasive tumors, which reflects the biological behavior of tumors as well as their clinical variables.U ovom istraživanju analizirao se utjecaj hormonskog receptorskog statusa, tj. estrogenskih (ER) i progesteronskih (PR) receptora na termografski nalaz kod bolesnica s karcinomom dojke. Rad je napravljen u KBC “Sestre milosrdnice” na Zavodu za onkološku kirurgiju i Zavodu za patologiju u suradnji s licenciranim stručnjacima za termografiju sa Zavoda za termodinamiku, toplinsku i procesnu tehniku Fakulteta strojarstva i brodogradnje u Zagrebu. Istraživanje je obuhvatilo 75 prijeoperacijski termografski snimljenih bolesnica s invazivnim tumorom dojke, starosti 36-86 godina, prosječne dobi 64±11,36 godina. Rezultati istraživanja su pokazali da je dojka s tumorom statistički značajno toplija (p<0,001) u odnosu zdravu dojku kod svih bolesnica. Nije bilo statistički značajne razlike (p>0,05) između bolesnica s pozitivnim u odnosu na one s negativnim estrogenskim receptorima. Za razliku od svih prethodno objavljenih rezultata različitih termografskih istraživanja invazivnih tumora dojke i utjecaja hormonskog receptorskog statusa na termografske nalaze, iz rezultata dobivenih u ovom istraživanju može se primijetiti da su ER- tumori imali višu maksimalnu i prosječnu temperaturu u odnosu na ER+. Primjetno je da su ER- tumori imali manji utjecaj na zagrijavanje cijele dojke, kao i to da je maksimalna i prosječna temperatura cijele dojke bila viša u ER+ tumorima. Aritmetičke sredine za maksimalne i prosječne temperature tumora statistički su značajno više kod progesteronski negativnih tumora u usporedbi s progesteronski pozitivnim tumorima (p<0,05). U zaključku, za razliku od ranijih termografskih istraživanja, rezultati termografske analize invazivnih tumora dojke u ovom istraživanju pokazali su da postoji razlika po utjecaju na termografske nalaze s obzirom na status hormonskih receptora. Ove rezlike ukazuju na danas dokazane različite imunohistokemijske, patohistološke i biološke osobine tumora dojki s obzirom na status hormonskih receptora