Field of the Invention

The present invention relates to a Hot Box for testing the thermal properties of the materials. More particularly, the present invention relates to an integrated multi-functional Hot Box for evaluating thermal transmittance and convective coefficients for building elements.

Background of the Invention

Thermal conductivity measurement is a very important part of material analysis in construction. In the construction industry, low conductivity is a requirement in building materials where insulation is an important consideration.

Thermal property measurement techniques include either the transient or steady-state instrumentation categories. In steady-state measurements, heat is applied to a sample, until constant temperature equilibrium is reached, while the transient method involves applying heat to a sample over a period of time and measuring the changing thermal response of the sample. There are a number of instruments available to measure thermal conductivity using steady-state methods. Some of these instruments include guarded hotplate, heat flow meter apparatus, thin heater apparatus, guarded comparative-longitudinal heat flow technique, etc.

The hotplate is a steady-state technique that involves placing a solid sample of fixed dimensions between two temperature regulated plates maintained at different temperatures. While steady-state methods are generally very accurate, they are also time consuming, taking hours to complete a single test. Also they are not suitable for non-homogenous materials and specimens with uneven or textured surfaces and/or with patterns/contours.

Further, the guarded comparative-longitudinal heat flow technique is restricted to only homogenous specimen's i.e. opaque solid specimens only. Another setup existing in the art that could test vertical and horizontal elements is a rotatable hot box that needs a 90° rotation for testing horizontal elements.

For the reasons stated above, which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for an improved integrated multi-functional Hot Box for evaluating thermal transmittance and convective heat transfer coefficients for building elements, under varying inclinations (vertical to horizontal).

Object of the Invention

The present invention has for an important object to provide a multifunctional calibrated guarded box for testing homogenous and non-homogenous building elements but not limited to masonry walls, cavity walls, roofing system, flooring system, doors, windows etc.

Another object of the invention is to provide an arrangement which can accommodate intended/designed undulations/textures on the specimen surface.

It is another object of the invention to provide an arrangement which enables to accommodate the guarded hot box features and the configuration of the set up facilitates its operation as double guarded hot box.

Yet another object of the present invention is to provide an arrangement to accommodate non-turbulent natural convective air-flow regimes and also to achieve non-turbulent passive convective air movement even for testing horizontal specimens.

Yet another object of the present invention is to provide an arrangement where data can be acquired under forced convective air-flow conditions and also, to evaluate the impact of both natural and forced convective air-flow on heat transmittance through the test element.

Yet another object of the present invention is to provide an arrangement to test elements up to 640 mm width which leads to test multiple configuration cavity walls with varying (ventilated & unventilated)cavities, including modern and traditional (vernacular) construction materials such as fly ash, stone masonry, cement-concrete, straw, rammed earth, adobe, etc for their thermal performance. Building elements comprising (dry and/or mortared) interlocking blocks would also be tested; varying mortar-masonry unit configuration could also be tested.

Yet another object of the present invention is to provide an arrangement for testing horizontal specimens dividing hot box into upper and lower halves, measuring heat transmittance downward across the specimen, by reversing the polarity of peltier system to enable its working as a heating unit for the upper half of the chambers.

Yet another object of the present invention is to provide an arrangement for simulating variable incident-solar conditions to measure solar heat gain through building elements

Yet another object of the present invention is to provide an arrangement which would provide real-time software support for detection of the steady heat flow conditions to determine the thermal transmittance.

The characteristics and advantages of the invention are further sufficiently referred to in connection with the accompanying drawings, which represent one embodiment. After considering this example, skilled persons will understand that variations may be made without departing from the principles disclosed and we contemplate the employment of any structures, arrangements or modes of operation that are properly within the scope of the appended claims.

Summary of the Invention

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.

Accordingly, an aspect of the present invention is to provide a hot box arrangement for measuring thermal transmittance characteristics of specimens. The apparatus comprises :a first chamber including a heating coil to dissipate consistent heat inside the first chamber, a second chamber including a peltier module based system to operate as cooling unit to extract heat generated by the first chamber (which could also be operated as a heating unit by reversing the polarity, for measuring thermal transmittance across horizontal specimens by heating upper half of the chambers) thereby maintaining a constant temperature gradient across the test specimen and a central frame including a base to support the specimen, wherein the specimen includes a plurality of thermocouples, and wherein the central frame is butted between the first chamber and the second chamber, wherein the heat generated in the first chamber is allowed to impose on the specimen placed at the central frame, wherein the imposed heat is absorbed and transmitted through the specimen to the second chamber, and wherein the plurality of thermocouples placed in the specimen are capable of measuring the temperatures (and consequent heat flows) at different sections across the specimen to obtain the thermal gradient data of the same, wherein directional and omni-directional hot-wire anemometers are placed in the chambers to record air-flow regimes close to the specimen surface and wherein anemometers would also be placed inside specimen cavities to record air-flow behavior.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

Brief description of the drawings

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

Figure 1 is a schematic representation of an arrangement for testing homogenous and non-homogenous building elements in accordance with the principles of the present invention.

Figure 2 is a schematic representation showing heat and air-flow pattern inside the chambers of the arrangement shown in figure 1.

Figure 3 is a schematic representation of double guarded hot box in order to enhance the control over heat losses to yield more accurate and reliable temperature measurements, transmittance and coefficient characteristics.

Figure 4 shows an example schematic representation of an arrangement including horizontal or inclined specimens.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

Detail description of the invention

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Figs. 1 through 4, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.

Figure 1 is a schematic representation of an arrangement for testing homogenous and non-homogenous building elements in accordance with one embodiment of the present invention. The arrangement designed as two nearly identical movable insulated enclosures i.e. a first chamber and a second chamber. The arrangement further includes a central frame to support the test specimen (walling or roofing systems) of varying configurations.

The arrangement has a housing (not shown in figure) to accommodate the arrangement as a double guarded hot box in order to enhance the control over heat losses to yield more accurate and reliable temperature measurements, transmittance and coefficient characteristics.

The first chamber includes a heating coil to dissipate consistent heat and the second chamber including a pettier module based system to operate as a cooling/heating unit to extract/supply heat. The second chamber is so arranged with the first chamber in order to maintain a constant temperature gradient across the test specimen. The central frame includes a base to support the specimen, wherein the specimen includes a plurality of thermocouples (not shown in figure), and wherein the central frame is butted between the first chamber and the second chamber. The specimen may be or may include homogenous and non-homogenous building elements but not limited to masonry walls, cavity walls, roofing system, flooring system, doors, windows etc.The heating coil connected to a power supply (not shown in figure) is mounted at the bottom inclined side of the hot chamber. The solid-state peltier module based system is installed or mounted at cut-outs made at the upper inclined side of the cold chamber to cool the chamber.

The two peltier modules, each are sandwiched between copper blocks which are attached to internal and external heat sinks with aluminum fins. Heat sink paste has been applied to the interfaces between heat sinks and copper blocks and also copper blocks and peltier modules. Both the heat sinks are supported with well-spaced wooden spacers for fixing it to the metal sheet body of cold chamber. The peltier modules are fixed to the top inclined side in the cold chamber so that any problem of water droplets dripping due to condensation would not affect the insulation.

The movable chambers are made of G1 sheets joined by riveting. The sheets have been joined such that the joints are confined only to the corners of the boxes. External stiffeners are provided on all sides to reduce any wobbling or distortion and to maintain the geometric and volume integrity of the boxes. The boxes are supported on wheels preferably made up of self-lubricating nylon, where the wheels are fixed with seated metal ball-bearings to the metal brackets supported with wide base provided at the bottom of the boxes so as to avoid any punching effect due to the point loads. In addition, rubber pads have been provided between the wheel brackets and the chamber to dampen any vibration effect due to movements. The arrangement is provided with handles for handling the chambers.

A latching with locking system is also provided to ensure tight closing of the two chambers to the central frame without any gap at the edges. An anti-corrosive spray has been applied in the riveted seams and at any location prone to removal of galvanized coating. The two insulated chambers, a PUF (Polyurethane Foam) layer of 75mm thickness is pasted inside the hot box using proprietary adhesive. For fixing, the panels cut to size are first made free of PUF powder or dust using vacuum cleaner so as to achieve good adhesion. The adhesive is applied as two coats, first coat being allowed to get absorbed into the PUF and dried. After the first layer is dried, a second coat is provided and left for 10-15 minutes to attain a sticky state. A layer of adhesive is applied on the metal sheet also and left to attain a tacky state before fixing the PUF panel. The metal sheet surface is roughened using sand paper prior to application of adhesive for better bonding. Extra care has been taken while applying adhesive to the panels for achieving uniform thin layer of paste and also to avoid any air cavities between the PUF insulation and metal layer while fixing. After fixing the PUF, it has been allowed to remain under pressure for nearly 24 hrs for good bonding with the metal layer. A final layer of aluminum foil is stuck to the PUF to have a smooth and low emissive surface inside the chamber. The PUF panels are cut to size such that the joints are confined to only corners. Only one of the sides has an intermediate joint. The joints between the PUF panels have been made at 45°, so as to avoid any invisible seams. Later these joints and the minute gaps are all filled with spray PUF to ensure proper insulation at joints and the sides. Two rectangular slots in the PUF are provided at the top inclined side of the cold chamber for fixing the cooling unit.

The central frame has a built-up section with the base formed by two structural Channel sections (400mm X 100mm) joined together by means of welded MS plate sections and remaining three sides with 100 mm angle sections at the edges with adequate gauge MS sheets fixed to them. The MS sheets are provided with holes for drawing thermocouple wires. Timber sections are provided all along the edge of the Central frame for both hot side and cold side for maintaining a specific gap between the boxes in the closed position. The central frame is provided with two layers of PUF both internal and external as an extra precaution to check any flanking loss through the sides of the specimen. The fixing of the PUF has been as mentioned earlier. As an additional precaution, use of spray PUF at joints and gaps has helped to get rid of any air gaps. The external PUF layer is covered with metal sheets to have PUF protection and also to have good finish.

In the central frame there is a provision for fixing and controlling set of length-adjustable nylon/metal rope/rods fixed to the top of the central frame to support and test inclined roofing elements (as shown in figure 4) which makes the whole arrangement unique as compared to other apparatuses.

A plurality of thermocouples placed at the specimen which is capable of measuring the temperature (and consequent heat flows) at different sections across the specimen from the first chamber to the second chamber in order to obtain consistent thermal gradient. Thermocouples would be used for temperature measurement at various locations on the surface of specimen, across the cross-section and inside the chambers. Thermocouples are also placed inside the specimen to get information on the temperature gradient across its width. The thermocouples are connected to a programmable digital data acquisition system for continuous real-time recording and downloading of the measurements including monitoring and storing in the computer. The experimental observations could also provide data for calculating the specific heat capacity of the test specimen. Three sets, each set comprising an ammeter and voltmeter, are provided ; one for the heating element to control and quantify the heat input and two for each of the peltier module in the cold chamber to check and control its operation and cooling potential. Anemometer would be placed in the chamber in order to measure the air velocity in the chamber and also within the specimen cavity(s) and linked to the same digital data acquisition system provided for temperature measurements.

Air velocity would also be measured for calculation of convective coefficient of the test element under natural convective air-flow regimes. The impact of ambient air velocity on the thermal transmittance of building elements would also be evaluated. Provision for forced air velocity is also integrated. Air velocity measurement also enables to check that the velocity inside the chamber is within specified limit. The test specimen can comprise building elements with varying material configuration, cavity configuration. The arrangement also includes an efficient data acquisition system for acquiring data from data loggers for further analysis.

In a working example embodiment for U value measurement: Specimens with thermal transmittance value approximately in the range of 0.1 to 340 W/m2K can be evaluated. The Hot side temperature can reach maximum of 80°C (353.15 K) and the Cold side temperature can reach minimum of 15°C (288.15 K)

For a test specimen:

1. Wall thickness range between 110 to 640mm, cavity wall up to 450mm wide

2. Roof thickness range between 110 to 220mm

3. Inclination of specimen from 0 to 90°

4. Surface texture of specimen - smooth, rough and textured and/or with patterned/contoured surface profiles with varying convective coefficients and surface emissivity

5. Forced convection air-flow velocity between 1 m/s and 2.75 m/s in excess of 5.5m/s.

Figure 2 is a schematic representation showing heat and air-flow pattern inside the chambers of the arrangement shown in figure 1. The arrangement as shown in figure 2 includes a first chamber, a second chamber and a central frame. The internal configuration of both the first and the second chamber is such that the end portion where the heating coil and peltier is arranged are intentionally made inclined at the top and bottom. This type of inclination enables free convective flow of air inside the chamber (indicated by arrowed line in Figure 2). Any other type of arrangement inside the chamber is also possible in order to conduct studies under forced air-flow regimes by propelling air directly onto the building specimen by means of fans.

Figure 3 is an example schematic representation of double guarded hot box in order to enhance the control over heat losses to yield more accurate and reliable temperature measurements, transmittance and coefficient characteristics.

Figure 4 shows an example set up of testing inclined specimens. The arrangement includes a fixing and controlling set attached thereby a length-adjustable supporting system, where the fixing and controlling set made of nylon/metal rope/rods is fixed to the top of the central frame for testing inclined specimens.

FIGS. 1-4 are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated, while others may be minimized. FIGS. 1-4 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.

In the foregoing detailed description of embodiments of the invention, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of embodiments of the invention, with each claim standing on its own as a separate embodiment.

It is understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein," respectively.

We Claim:

1. A hot box arrangement for measuring thermal transmittance characteristics of a specimen, the apparatus comprising:

a first chamber including a heating coil to dissipate consistent heat inside the first chamber;

a second chamber including a cooling system to extract heat generated by the first chamber thereby maintaining a steady temperature gradient; and

a central frame including a base to support the specimen, wherein the specimen includes a plurality of thermocouples, and wherein the central frame is butted between the first chamber and the second chamber,

wherein the heat generated at the first chamber is allowed to impose on the specimen placed at the central frame, wherein the imposed heat is absorbed and transmitted through the specimen to the second chamber, and wherein the plurality of thermocouples placed at the specimen are capable of measuring the temperatures and consequent heat flows at different cross-sections of the specimen to obtain the thermal gradient(s)..

2. The arrangement as claimed in claim 1, wherein the first chamber and the second chamber are insulated movable chambers and are made up of G1 sheets joined by riveting.

3. The arrangement as claimed in claim 1, further includes additional housing to accommodate the arrangement in order to enhance the control over heat losses to yield more accurate and reliable temperature measurements.

4. The arrangement as claimed in claim 1, wherein the specimen includes homogenous and non-homogenous building elements but not limited to masonry walls, cavity walls, roofing system, flooring system, doors, windows etc.

5. The arrangement as claimed in claim 1, wherein the first chamber and the second chamber are arranged such that in order to achieve non-turbulent passive natural convective air movement including testing of horizontal specimens.

6. The arrangement as claimed in claim 1, wherein the second chamber is capable of maintaining consistent cooling of air volume in the chamber.

7. The arrangement as claimed in claim 1, wherein the measurement of temperature within the specimens to understand the thermal gradient across the width of the specimen and for estimation of its specific heat capacity, and wherein the measurement of temperature and air velocity within the chambers for evaluation of convective heat transfers co-efficient under both natural and forced air-flow conditions and also the impact of varying air speeds on transmittance.

8. The arrangement as claimed in claim 1, further including a fixing and controlling set attached thereby a length-adjustable supporting system, wherein the fixing and controlling set made of nylon/metal rope/rods is fixed to the top of the central frame for testing inclined specimens.

9. The arrangement as claimed in claim 1, further includes provision for measuring thermal transmittance across horizontal specimens by heating upper half of the chambers by enabling the peltier system to operate as a heating unit by reversing its polarity.

10. The arrangement as claimed in claim 1, further including a power supply for providing dedicated DC power for the heating arrangement or coil in the first chamber and two solid-state peltier modules in the second chamber.

11. The hot box arrangement for evaluating thermal transmittance characteristics of specimens substantially as herein described with reference to the accompanying drawings.