TROPICAL SUBTROPICAL GREEN BUILDING ALLIANCE CONFERENCE 2012 Humidity Control in Tropical Climate with Heat Pipes - The GREEN Way Case Study: Cheras Rehab Hospital, Kuala Lumpur By Mohan Dhingra Managing Director InviroTech Systems Sdn Bhd
We spend 80% time indoors at home at work or in the car so we are mostly Indoors.. An average adult consumes about 5000 gallons of air daily which is 4000 gallons of indoor air. Quality of air we breath is of paramount importance
High Humidity is among top three factors that affect Indoor Air Quality
Humidity level in the air is detrimental for: 1. Indoor Air Quality Leading to Health Concerns 2. Product Quality Due to moisture absorption 3. Industrial Processes Issues with Product Characteristics 4. Building Aesthetics due to growth of Mold & Fungus
Universally accepted design condition for Indoor humidity in comfort applications is at 55% RH @ 23-24 o C Room Temperature As the room set point is raised to 24 o C to save cooling energy, the indoor RH is likely to assume more importance than if the room was at 23 o C
Continued high levels of indoor RH can lead to large scale infestation of buildings with mold and fungus, which can render buildings unfit for occupancy.
Some who ignored humidity problem till very late RM 12.8 million: cost of clean up of mold infested hospital in Johar Bahru, Malaysia September 2004 Malaysia News Sources Toxic Mold in Kaweah Delta Hospital in Visalia, USA closed a staff lounge January 2001, nl.newsbank.com Asthma Blamed on Mold March 1964, The Miami News
Why Is Humidity Control Ignored till too late? High Humidity causes uneasiness among occupants when it reaches very high levels of about 80-90% RH. But constant 65-75% RH leads to growth of mold & fungus. Only when green & black patch begin to appear, also causing foul smell, people notice and complain. But by then, it is too late, and remediation is neither easy nor cheap.
Tropical Climate Typically Hot & Humid
Tropical Climate: Hot & Humid Outdoor Temperature ( o C) Incidence Hours in 1 Yr (Hrs) Delta T (OA IDC) ( o C) % of Hours in a year 20-22 12 22-24 802 24-26 3179 Not exceeding 4 o C 66% 26-28 1748 28-30 1312 4 to 7 o C 15% 30-32 1208 32-34 478 More than 7 o C 19% 34-36 21 Total 8760 For 81% of the time, aircon System is operating at far lower heat load demand than design parameters. Lesser heat load means lesser moisture removal in simple and conventional aircon system.
Typical design T for Aircon Systems: T OA T RM = 33 o C - 24 o C = 9 o C OA = Outdoor Air RM = Room Air > 30 o C > 30 o C > 30 o C 28-30 o C For 66% of time OA Temperature is < 28 o C 28-30 o C For 15% of time OA Temperature is b/w 28 30 o C 28-30 o C For 19% of time OA Temperature is > 30 o C < 28 o C < 28 o C < 28 o C T (T OA T RM) > 4 o C T (T OA T RM) = 4 o C - 7 o C T (T OA T RM) = > 7 o C
Tropical Climate - More Humid than Hot At 23 o C and 55% RH, the targeted room dew point is 13 o C 97% of the time the Outdoor Dew Point lies between 22-28 o C. 24.8 o C-35.6 o C, 1% 21.5 o C-22.2 o C, 2% Humidity load on aircon may fluctuate, but always remains high. Therefore, there is constant need for significant moisture removal capacities. 22.2 o C- 24.8 o C, 97%
Humidity Problems Common to Tropical Climates Weather: Most of the time, moderately hot & always very humid Typical conventional aircon systems are geared to respond to changing heat load demand For 81% of time aircon systems are operating as Oversized for prevailing heat load. This leads to turned down coil capacities, higher supply air temperatures and consequently lower moisture removal, at the coil. RESULT: Higher Indoor RH during low ambient temperature.
Cooling and Dehumidification Process over a cooling coil 1 2 2 Air Entering Cooling Coil Air Leaving Cooling Coil at full load. Air Leaving Cooling Coil at part load 2 2 1 M1 M2 M2 T2 T2 T1 Higher supply Air temperature to room means more moist air being fed to room
Reheat: Adding heat to maintain RH For constant air volume systems, at reduced demand heat load, artificial heat is created (added) to enhance the cooling process at cooling coil and therefore achieve higher moisture removal from air. Since this heat is added after cooling coil, it is called Reheat Adding Heat in an aircon system that is supposed to cool! Ironical! Isn t it? But needed to get the RH right.
Conventional choices for Reheating a) Electric Heaters b) Hot Water Coils c) Steam Coils The GREEN & Energy Efficient Alternative: HEAT PIPES
Heat Pipes installed in Air Handling Units are an ideal solution to Humidity Control
Heat Pipe How it works?
Heat Pipe How it works? (cont ) Heat Pipe is a U shaped heat exchanger that hugs the cooling coil of an Aircon from two sides. These sections encounter same air stream twice and provide pre-cooling & reheating in sequence. At Evaporator (located before cooling coil): Heat is removed from air stream leads to less sensible cooling required at coil, providing more latent capacity and enhances dehumidification. Now over-cooled air passes across reheat section of Heat Pipe, bringing the supply air temperature to a condition which meets the temperature level in accordance with sensible load of the room.
Heat Pipe: Psychometrics 1 : Outdoor Air Condition 2 : Room Design Point 3 : Mixing Point (FA + RA) 3-4 : Pre-Cooling by Heat Pipe 4-5 : Cooling and Dehumidification (coil) 5-6 : Reheating by Heat Pipe 6-7 : Heating due to Fan 7 : Room Entering Condition 4 3 2 1 5 6 7
Green Rating given to Heat Pipes according to Green Pages Malaysia
Case Study Cheras Rehab Hospital, Kuala Lumpur, Malaysia: 'Right' from Day 1
Case Study: Hospital IN KL, Malaysia High Humidity Concerns for Hospitals - Patients at hospital have low resistance to infection and more prone to allergies caused by mold & fungus (Hospital Acquired Infections) - The hospital equipment needs to be kept clean and germ free - Laboratories and Pharmacy have moisture sensitive material - Surgeons demand for cooler and drier operating room conditions due to the multiple clothing they wear
Case Study: Hospital IN KL, Malaysia (Cont ) Proposed Solution: - Heat Pipes to be installed in all 22 AHUs of the Hospital - Proposed Cost of Installation 3-4% of Total Air Conditioning Cost (Yes! It s that low!!!)
Case Study: Hospital IN KL, Malaysia (Cont ) Actual Solution Implemented : - Heat Pipes installed in 9 AHUs of the Hospital for 24 hours operation - No Heat Pipes installed in Day-only AHUs
Results were heart warming for everyone involved AHU Airflow (CFM) Reheat KW Saved (RM) Pre-cooling TR Saved (RM) Total Electricity KW Saving (RM) 1 3,643 23,066 7,849 30,915 2 2,690 17,558 6,197 23,754 3 3,510 22,033 7,436 29,469 4 11,110 75,050 25,614 100,664 5 1,999 21,345 7,436 28,781 6 11,995 102,592 35,115 137,707 7 2,619 23,066 7,849 30,915 8 2,790 17,902 6,197 24,099 9 2,790 17,902 6,197 24,099 Total Saving p.a RM 430,404 USD 134,953
RH Level with Heat Pipe Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ±5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ±5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
Consistent 55 ± 5% RH in all 9 AHUs with Heat Pipes
RH Level with Heat Pipe during Rain 55% ± 5% RH maintained even during rains
RH Level with without Heat Pipe AHUs without Heat Pipes will achieve RH as the room load comes closer to design and weather peaks to 35 o C
Applications where RH Control is of Hospitals Hotels Laboratories Pharma Industry Food & Beverage Storage & Packaging Rooms Libraries & Data Centres Electronic Industry Auditoriums & Museums Importance
Heat Pipes play a vital and critical role of humidity control in Buildings with futuristic air conditioning technologies like Chilled Beam, Chilled Slab Systems and UFAD Systems
Our Green Projects 1st GBI Platinum Building ST Building (27.4.11)
Walk that EXTRA mile. Heat Pipes provides is a Green & Safe Solution to Humidity Control