Barcol-Air BRM Radiant Module

Transcription

1 Barcol-Air BRM Radiant Module

2 General The high capacity Radiant Cooling Module BRM is based on the principles of the radiant cooling technology. Due to the purpose designed profile and the geometry of the unit an increase of convective cooling capacity is achieved. Even at the highest cooling capacity the comfort is never jeopardised, in fact, the severe standards of DIN 1946 part and SIA concerning the air velocity are strictly observed. Application.1. The Design of the Ceiling Installation Details The BRM can be mounted by using adjustable quick hangers either directly from the building ceiling or suspended from an installed ceiling grid. The weight is ca lb/ft. For the connection of the BRM to the hydraulic system and the connection of the elements in series, all metal flexible bellows type hoses (no oxygen permeability) are available. The flexible hoses are provided with high quality push-on couplings. In order to use the push-on couplings together with the installed armatures a specially designed nipple is available. The BRM unit offers a wide range of applications. It can be installed in offices and conference rooms, as well as in shopping centers and laboratories. The BRM can be used as a spot cooling element or a cooling band arranged in strips or simply as a chilled ceiling. Typical Design The extruded aluminium profile is optimally formed to accomodate the copper tube and to provide two cooling fins which are rounded off at the outer end. The surface is black anodized and can be painted if desired. The profiles are 5 in wide fig..1. The gap between the profiles is 0.6 in. Units up to 10 profiles wide and max. 98 in long can be supplied. Copper tubes 1 mm O.D. are used. The high precision of the tube and the extruded profile safeguard a continuous contact between the two surfaces throughout their entire length, thus creating an optimal heat transfer. The Radiant Cooling Units BRM are assembled in the works to form an element ready for installation and connection to the hydraulic system. (fig..) There are numerous possibilities regarding the arrangement of the ceiling.where a metal ceiling is planned or already in existence, the BRM elements can be installed either above the perforated ceiling or directly integrated in the ceiling design. In both applications the thermal storage capacity of the building substance (concrete) can be used. If there is no metal ceiling planned the BRM can be installed directly below the concrete ceiling to represent an architecturally pleasing arrangement. Dimensions Fig..3 shows the unit width in inches and the active area in ft for different length and numbers of profiles Number of Profiles ; Width 3 of Module (in) 30 3 ; ; ; ; ; ; ; ; Active Area of the Module (ft²) Length of Module (in)

3 How to Determine the Standard Cooling Capacity Fig. 3.1 shows the cooling capacity line, determined in accordance with the FGK standards, part KD1 as well as the DIN 4715 standards part 1, as a function of the mean temperature difference t m.the standard cooling capacity is related to an application with the following conditions:. a room height of 3.3 ft. 30% active area. the BRM installed 8 in below the concrete ceiling. an asymmetric arrangement of heat sources in the room. thermal storage capacity of the building substance must not be considered. the copper tube diameter is 1 mm How to Determine the Mean t m: t m = t R (( t WI + t WO )*0.5) t m = mean temperature difference R t R = room air temp. F (dry bulb) t WI = temperature water inlet F t WO = temperature water outlet F Whenever the temperature difference between room air and water outlet temperature is very small, one has to use the logarithmic instead of the arithmetic average temperature difference between room air and water outlet temperature t m = (t WO - t WI)/ln ((t R - t WI)/(t R - t WO )) Applications The influence of the ceiling coverage on the capacity is calculated with the following formula: q B = q* f B q B = specific cooling capacity at the calculated ceiling coverage q = specific cooling capacity as shown in diagram fig. 3.1 = correction factor f B Ceiling coverage in % Factor f H 0% % % % % % % % Cooling Capacity based on the Active Area (Btu/h*ft²) Whenever a metal ceiling (50% free area) at a distance of ca. 4 to 8 in is installed below the BRM, the capacity has to be reduced by the factor f Dd = Mean Temperature Difference Δtm ( R) (Room Air Temp. - Average Chilled Water Temp.) 3

4 How to Determine the Pressure Loss of the Copper Tube 1 mm Dia The diagram in fig. 4.1 shows the resistance of one aluminium profile with a copper tube of 1 mm diameter as a function of the circuit water volume and the length of the profile. In order to determine the total circuit resistance, the value derived from the diagram must be multiplied by the number of BRM and the number of profiles per BRM connected in series and added to the resistance of all flexible hoses in the circuit. p tot = ( p 1 * n U* n P ) + p C p tot = total resistance of the circuit p 1 = resistance of one profile according to diagram 4.1 n U = number of BRM in series n P = number of profiles on each BRM p C= resistance of the flexible connectors, as indicated in the section Hydraulic Minimum Water Flow In order to obtain turbulent flow conditions the water quantity of the circuit should not be below 0 gal/h for the 1 mm tube. This can be achieved by connecting the necessary number of panels in series. In situations where turbulent flow can not be achieved, the specific cooling capacity must be corrected accordingly. 4.1 Resistance of One Heat Conducting Rail (psi) Length of Heat Conducting Rail (in) Water Quantity (gal/hr)

5 Hydraulic Circuits When planning the chilled water distribution it is preferable that the water circulation through the active area is from the window area to the centre of the room. Due to the large tube cross section used on the modules it is possible to connect all modules of one zone in series. This means that only the first and the last module of the zone must be connected to the mains. The water connections to the mains are in accordance with the room or zone layout. Large rooms or large zones active areas should ideally have the same number of modules in series (equal water distribution). In cases where this is not possible the individual water circuits must be adjusted with appropriate throttling devices, see fig. 5.1 pos.1. Generally it is recommended that the individual water circuits of the active areas should be isolated from the mains by means of a ball type valve on the water inlet and outlet branch, see fig. 5.1 (Pos. 3 and 4). The advantages of this method are particularly useful during commissioning work or where alterations have to be made at a later date. During commissioning, the main water installation can be pressure and leak tested with closed ball valves and changes in an active zone can be done without draining the complete system. The control valves regulate the water quantity in the active zone dependent on the cooling requirements. An inline valve is sufficient for most applications. For further information see section Controls in this brochure. For the connection of the BRM to the mains inlet and outlet as well as the inter connection of the BRM in series, all metal flexible bellows type hoses are available, see fig. 5.1 (Pos. 5 and 6). No oxygen can permeate through the all metal flexible hoses into the chilled water. The flexible hoses are provided with high quality push-on couplings. In order to use the push-on couplings together with the installed armatures a specially designed nipple is available, see Fig. 5.1 (Pos. 4) water volume distribution valve control valve 3 ball-type isolating valve with/without air vent/draining valve 4 nipple hose with push-on couplings with push-on couplings 5

6 Details of Hydraulic Components Control of Chilled Ceilings Fig. 6.1 shows the flexible all metal bellows type hose with push-on couplings at both ends. No oxygen can permeate through the hose into the chilled water circuit. Technical Data of the All Metal Hose stainless steel material code push-on coupling: Legris DN 1 max. operating pressure: 130 psi dimensions: DN 10 x 40 in long Cv - value 1.13 How to Calculate the Resistance of One Hose When fitting the push-on coupling onto the copper tube end, the unit is lined up with the tube and using light pressure, pushed in the direction of the tube until it has reached the tube stop. When dismantling, the release ring (3) is pushed in the direction of the coupling (disengaging the segment ring) and the flexible hose can be pulled off the copper tube. Attention: The coupling must only be disconnected after the zone pipework has been drained. given: all metal flexible hose Cv-value = 46.7 ft3/h, L=39.7 inch, DN=10, bend 180, water volume m= 1.13 gal/h Fig. 6.3 shows the screw-in nipple which can be tightened and screwed into the 1/ BSP thread of the isolating valve using appropriate sealing materials. The stud is machined (1 mm dia.) to receive the push-on coupling of the connecting hose. The nipple can be used on both sides, the water inlet and outlet. UNKNOWN: Resistance p p= (m/cv)x100 = (1.13/46.7)x100 = 0.85 Pa Fig. 6. shows the push-on coupling which has been specially designed for use with chilled ceilings. The seal is achieved by means of a double profile ring. The coupling hooks on to the copper tube using a segment ring made of stainless spring steel. The advantage of this push-on coup- ling is found in a very simple, reliable connection and disconnection as well as in the superb production quality. To balance the water quantity of the different active zones, standard balancing valves with connectors for measuring equipment can be installed. With regard to control valves, see section Controls bellows type hose push-on coupling 3 segment ring made of stainless steel 3 dismantling release ring 6 Where variable internal and external heat loads prevail, the cooling output of a chilled ceiling is varied with the aid of a simple room controller. Normal control is achieved by throttling the water flow. The relatively small water content and the optimal selection of the material used on the BRM ensure a fast reaction to any changes in heat load. The resulting control characteristics are comparable with those achieved with air systems. Normally the algorithm PI-reaction is selected with a proportional band of l.8 R and an integral time of 10 minutes. Using such control, large heat load changes can be corrected quickly with stable results. An unintentional drift of the room air temperature, which would negatively influence comfort does not therefore occur. In order to achieve a stable control circuit, the correct sizing of the control valve is important. It is recommended that the valve authority is between 0.5 and 1. This means that the pressure drop, when the valve position is fully open, is equivalent to factor of the pressure drop calculated for the zone circuit. To avoid sedimentation it is recommended not to install valves with Cv values smaller than 35 ft 3 /h. In zones where more than one control valve is installed, care should be taken that all valves operate in parallel. 6.3

7 7.1 N zone controller B1 room temperature sensor B dew point sensor B Y1 Y1 Y1 chilled water valve Y heating valve Commissioning Pressure Testing Like all hydraulic systems used in buildings, the chilled ceiling systems must be tested for possible leaks and tested to withstand the working pressure. These tests must be done prior to commissioning, observing the local rules and regulations. heating 100 % 0 % - room air temperature + 7. cooling valve shut when saturation point is reached data line from previous rooms To avoid condensation, the chilled water temperature must always remain above the dew point of the room air. This must be achieved by the consequent control of the chilled water flow temperature. To eliminate any possibility of condensation, it is recommended to install a dew point sensor into each zone as a safety precaution. Prior to N B1 t Y data line to the following room reaching critical saturation, the sensor would react and as a result the control valve would prohibit any water circulation in the zone. Y Operational Testing To achieve correct operation of the BRM, the system must be carefully vented. Furthermore, proof of water flow through all pipe work including the BRM tubes is essential. The use of modern infra-red camera systems with image recording capacity provides a professional solution. The infra-red image print-out should be part of the commissioning manual. Fig. 7. shows a typical thermal image of BRM units in operation installed above a metal ceiling with 50% free area. 7

8 Contacts Headquarters Barcol-Air Ltd. 115 Hurley Road Oxford, CT Phone: (03) Fax: (03) Website: Barcol-Air Ltd. Georgetown Center, Building B 5963 Coreson Avenue South Seattle, WA Seattle@barcolairusa.com Website: Your partner for radiant cooling and heating, chilled beams and VAV systems.