Rotary Heat Wheel (Rotary Enthalpy Wheel) Introduction SAIVER cooperates with Heatex a leading Sweden Heat Exchanger Specialist to provide a compact and high efficiency rotary heat wheel for our worldwide clients. This document would cover a lot of information about rotary heat wheel. operation manual as well as some useful hints. It includes technical data, Selection of Rotary Heat Wheel To select the heat wheel, several parameters are needed to consider at the same time Efficiency Efficiency is an important consideration when using rotary heat wheel. However, there are three different efficiency terms are commonly used together with rotary heat wheel. a. Temperature efficiency calculated based on temperature b. Humidity efficiency calculated based on moisture content c. Enthalpy efficiency calculated based on enthalpy Usually, temperature efficiency is the highest one. The temperature efficiency should be higher than 60%. Please take note that exhaust side efficiency is different from supply side. The efficiency is related to face velocity as well as the contact area of wheel. efficiency, a bigger wheel or a wheel with a smaller channel height is needed. Efficiency Size of Wheel Channel Height To achieve higher Version: 2 Page 1 of 7
Pressure Drop Pressure drop will affect the bearing life as well as the fan power consumption. The recommended pressure drop is 100 to 200Pa. The pressure drop is related to face velocity. To minimize the pressure drop, a bigger wheel or a wheel with a higher channel height is recommended. Size of Wheel Channel Height Pressure Drop Design Consideration There are some few points must be noted when selecting heat wheel: a) Exhaust air volume should be equal to supply air volume To achieve the best performance, return air volume should be equal to supply air volume. Due to air balancing, it is not always achievable to have an equal return and exhaust air volume. In such case, supply air volume should not be less than 70% or more than 150% of exhaust air volume. b) Cross-contamination is possible Cross-contamination is a general term when either or both carryover and leakage occurs. Carryover occurs as air is entrained within the volume of the wheel and is carried into the other airstream. Usually carryover from exhaust to supply is unwanted, a purge section can be installed to reduce this phenomenon. Leakage occurs because the differential static pressure across the two airstreams drives air from a higher to a lower static pressure region. Therefore, pressure potential of supply air should be larger than exhaust air. It can be minimized by placing the fans so that they promote leakage of supply air to exhaust air. The best arrangement is draw-through for both air streams. Version: 2 Page 2 of 7
Controls There are two common control methods to control heat wheel. a) Variable wheel rotational speed control The wheel rotational speed can regulate the energy recovery rate. Various motor speed control methods are applicable. Using frequency inverter is getting popular because frequency inverter is getting cheaper. Transfer Efficiency Heat Transfer Moisture Transfer EA T r RA T F Ts FA SA Wheel Rotation Speed (RPM) b) Supply air bypass control Bypass Damper Supply air bypass control requires a supply air bypass damper to regulate a certain amount of supply air bypass Wheel (Face) Dampe Tr the wheel to achieve the desirable the supply air EA RA temperature. The bypass duct branch must have the Damper Actuator same pressure drop as the wheel and associated duct system in order to avoid air FA To Ts SA flow rate balancing problems. Version: 2 Page 3 of 7
Control Strategies There are several common control strategies to control heat wheel. a) Supply air temperature (T s ) control It is the simplest control strategy. A supply air temperature is set and one temperature sensor is needed to provide a feedback. The wheel speed increases and decrease until the desired temperature is reached or until the wheel reaches its minimum / maximum speed. b) Temperature comparison (T o & T r ) Two temperature sensors are used to measure the outer air and the exhaust air. The temperature differential ensures that the wheel only operates when the wheel is economically beneficial for treating the supply air. When the temperature of the outer air is lower than temperature of the exhaust air and cooling is needed, the wheel will stop. c) Enthalpy comparison (h o & h r ) When humidity control is considered, two enthalpy sensors are needed. When the enthalpy of the outer air is lower than enthalpy of the exhaust air and cooling is needed, the wheel will stop. Technical Information To, ho Ts Fresh air Supply air Tr, hr Extract air Return air The Heatex Model W is a rotary heat wheel for HVAC heat recovery application. Significant for the Model W is, the well achieved roundness / balance of the wheels. Also to be noted, are the smooth and leveled air in- and outlet sides. In order to prevent unwrapping, the Model W is as standard provided with spokes. The performance of the Model W is integrated with SAIVER state-of-the-art selection program. Model W is available in four different standard materials: aluminium, aluminium with epoxy coating, aluminium with hygroscopic surface and aluminium with sodium silicate coating. Version: 2 Page 4 of 7
Three different channel heights are available: 1.5mm high efficiency but higher pressure drop 2.0mm standard 2.5mm suitable for more polluted exhaust air Wheel outer Power supply Casing dimension Motor power (W) Weight (kg) diameter (mm) (mm) W/o coating With coating 1.5mm / 2.0mm / 2.5mm 500 220V/1Φ/50Hz 600 x 600 x 265 25 25 36 / 32 / 31 600 220V/1Φ/50Hz 700 x 700 x 265 25 25 44 / 39 / 36 700 220V/1Φ/50Hz 800 x 800 x 265 25 25 53 / 45 / 42 800 220V/1Φ/50Hz 900 x 900 x 265 25 25 62 / 53 / 49 900 220V/1Φ/50Hz 1000 x 1000 x 265 25 40 73 / 62 / 57 1000 380V/3Φ/50Hz 1100 x 1100 x 265 40 90 85 / 71 / 65 1100 380V/3Φ/50Hz 1200 x 1200 x 265 40 90 125 / 108 / 100 1200 380V/3Φ/50Hz 1350 x 1350 x 265 90 90 151 / 130 / 121 1300 380V/3Φ/50Hz 1450 x 1450 x 265 90 180 168 / 144 / 134 1400 380V/3Φ/50Hz 1550 x 1550 x 265 90 180 187 / 159 / 147 1500 380V/3Φ/50Hz 1650 x 1650 x 265 90 180 207 / 174 / 161 1600 380V/3Φ/50Hz 1750 x 1750 x 265 90 180 228 / 191 / 175 1700 380V/3Φ/50Hz 1850 x 1850 x 265 180 180 254 / 212 / 194 1800 380V/3Φ/50Hz 1950 x 1950 x 265 180 180 277 / 230 / 210 1900 380V/3Φ/50Hz 2050 x 2050 x 265 180 250 301 / 249 / 226 2000 380V/3Φ/50Hz 2150 x 2150 x 265 180 250 327 / 268 / 244 2100 380V/3Φ/50Hz 2250 x 2250 x 265 180 250 353 / 289 / 261 2200 380V/3Φ/50Hz 2350 x 2350 x 265 180 250 381 / 310 / 280 2300 380V/3Φ/50Hz 2450 x 2450 x 265 180 370 409 / 332 / 299 2400 380V/3Φ/50Hz 2550 x 2550 x 265 180 370 439 / 355 / 319 2500 380V/3Φ/50Hz 2650 x 2650 x 265 180 370 470 / 379 / 340 Version: 2 Page 5 of 7
The Wheel Material and dimensions Rotating wheels are available in four different standards: aluminum, epoxy coated aluminum, aluminum with a hygroscopic surface and aluminum with sodium silicate coating The depth of the wheel is 200mm Maximum diameter is 2500mm Wheels in epoxy coated aluminum have edges that are self sealed in corrosive environment Aluminum and epoxy coated aluminum wheels are recommended to rotate 10rpm Aluminum with a hygroscopic surface and aluminum with sodium silicate coating wheels are recommended to rotate 17rpm Wrap and hub are manufactured in aluminum Lifetime for a ball bearing is 50,000hr Casing General For wheels from 1101mm in diameter there is an extra girder mounted which makes the casing looks like a T viewing it from the back and front side Brush sealant is assembled at the wheel pressing on the casing from the inside to minimize the cross contamination Brush sealant is assembled at the girder as well which separate the two air streams at the back and the front of the casing to minimize the cross contamination Casing material is galvanized iron Purge Sector (Option) The purpose of the purge sector is to clean the wheel from the exhaust air before it turns over to the supply air side The purge sector is made in the size of 5 with start at center of the wheel At the purge sector is brush sealant assembled at the upper side and at the lower side At order please fill in position of purge sector according to enclosed guideline. The position is fixed based on the direction of the wheel as well as the directions of the supply/exhaust air. Version: 2 Page 6 of 7
Drive Motors for constant speed are as standard delivered in two types. - 1 x 230V - 3 x 380V Casings up to and including 999mm in square are delivered with 1x220V motor. Casings from 1000mm in square are delivered with 3x380V motor Maintenance and Cleaning of Rotating Heat Exchangers Maintenance Of The Wheel To secure the function and performance, the face of the wheel has to be inspected regularly for dust and dirt. This dirt or/and dust is recommended to be removed by different techniques. For only a small amount of easy removable dirt use a vacuum cleaner is recommended. For heavier dirt it is also possible to use compressed air but with caution. Finally, firmly dirt at the wheel are easiest removed by using hot water and a mild detergent. Maintenance Of Drive Unit Tension of the V-belt must be checked after the first 100 hours in operation to secure the rotational function of the wheel. To adjust tension check the belt tensioner as first step and adjust it as much as possible. As second step shortening the V-belt. The V-belt is put together with an easy removable mechanical lock but do not forget to adjust the belt tensioner after this operation. The round belt is self tensioned and should not be needed to adjust. Maintenance Of Brush Tightness between brush sealants and casing has to be checked during inspection. The brush sealants are easily adjusted by loosen the screws and move the brush sealant into the right position. V-belt, Round belt and brush sealants are all available as spare parts. Version: 2 Page 7 of 7