Radiant Cooling

For cooling applications, the building mass (floor, ceiling and walls if necessary) is cooled, which forms a sink to absorb energy from the higher level. The human bodies and all other objects in the premise are the source of heat with higher energy level; reverse for heating applications as well. Heat is automatically transferred from the hot objects to the colder surrounding, making the human bodies comfortable. Eventually the air temperature also reduces due to conduction & natural convection. Basic scientific principle same as structural cooling, except this system used chilled water from a conventional refrigeration system Basic Principle

Plastic pipes concealed in ceiling/False ceiling/floor/slab/walls. Chilled water is circulated through the concealed pipes. Plastic pipes can be covered with all usual building materials. Perceived temperature: numerical average of mean radiant temperature of surrounding surfaces and the room air temp Basic Principle

Types There are three types of chilled beam systems: – Chilled ceiling /floor/slab/wall – They work by means of convectional heat transfer, and induce air movement in the room in which they are placed. The sensible cooling capacity is approximately 24 BTU/hour per suare foot of beam. Chilled ceilings lack the ability to control the humidity of a room and must be paired with a ventilation system. – Passive chilled beam – Passive beams use a pipe surrounded by a coil in order to form a radiator system, often used in conjuction with an under-floor air distribution system. The cooling capacity is approximately 400 BTU/hour per linear foot of beam. These too do not have any method for maintaining the humidity of a room, and must be paired with a ventilation system. – Active chilled beam – They have a ventilation air ducted through the chilled beam. The ventilation air must first be de-humidified upstream of the passive chilled beam, to avoid condensation potential at the chilled beam.

Types Chilled Floor Systems

Types Chilled Floor Systems

Types Chilled Floor Systems

Types Floor Cooling Systems

Types Chilled Floor Systems

Types Chilled Ceiling Systems (Panel Type)

Types Chilled Ceiling Systems (Panel Type)

Types Chilled Ceiling Systems (Plastered Ceiling)

Types Chilled Ceiling Systems (Plastered Ceiling)

Types Slab Cooling

Types Slab Cooling

Types Slab Cooling

Types Wall Cooling

Operation Schematic Variable Primary Pumps Chillers Radiant Cooling surface Pressure independent balancing cum control valve CWS – 61 deg F C WR – 6 9 d e g F De-coupler Valve CHW Return Temperature sensor ZONE controller ZONE temp sensor ZONE Humidity sensor CHW supply Temperature sensor ZONE VAV of DOAS Surface temp sensor

Types Chilled Floor Systems DescriptionVariables Out put, upward34 W/sqm Output, down ward (Loss)10% 3.4 W/sqm Spacing100mm Loop Length150M Loop Area(Loop Length X spacing)/ X 100/1000 =15 Sqm Total Output per Loop, W34 X *15 = 561 Watt Pipe Dia MM Pipe Spaci ng, mm Outpu t Upwar d W/sq m Loop Lengt h M Loop Area Sqm Flow Kg/Hr Pr.dr op Loop (Kpa) Flow rate, Kg/Hr=Total watt/(4.2X1000 X Delta T)X /(4.2X1000X4) X3600= 120 Kg/Hr Loop pressure drop, KPa=Kpa/M X Loop length =0.09*150 = 13.5KPa

Types Radiant Cooling - Comparison of Cooling Out System TypeCooling Output (w/sq.m) Floor Cooling34-42 W/sq.m Wall Cooling47 W/sq.m Plastered Ceiling Cooling58 W/sq.m Slab Cooling68-72 W/sq.m Ceiling Panel Cooling74-84 W/sq.m

A.Energy and Operation Costs Specific Heat Capacity of water ~ 4 times that of air: for the same flow rate, 4 times more heat can be removed by using water than by using air. Air flowrate and Fan power consumption reduced drastically : To remove 1 kW of heat from a room, an AC needs ~140 W of fan power. For the same load, a radiant system needs ~ 3 W to run the circulation pump. Reduced energy loss due to duct leakage & fan motor heat loss Lower life cycle cost compared to conventional, due to decreased maintenance With every degree increase of room temp of the AC system, about 6% of energy is saved Benefits ParameterAC-Only SystemRadiant System Mean Radiant TemperatureNA20 0 C Room Air Temperature24 0 C28 0 C Perceived Temperature24 0 C Reduced Energy0% (i.e. 6 % x 0 0 C)24% (i.e. 6 % x 4 0 C)

Benefits Supply temperature – 7 0 C Return temperature – 12 0 C COP – 3.22 Supply temperature – 15 0 C Return temperature – 20 0 C COP – 4.17 Higher chiller operating temperature improves COP by ~ 30%

B.Capital Costs & Sale-able Space It has lower first costs attributed to integration with structure and design elements and smaller chiller requirement. Low air volume and hence duct sizes are significantly reduced. Fewer Air Handling Unit; in some cases, only treated fresh air units may be required. AHU room in the building can be eliminated Additional floor can be added in same FSI / Building Height due to vertical-space saving from eliminated ducts Space saving from smaller chiller size Benefits

C.Other Space heating can be done using the same system Absolutely noiseless & vibration free Does not produce any draft. Provides uniform temperature Surface temperature or supply temperature is always above dew point and hence, no chance of condensation Benefits

Constraints Surface temperature should not be equal or below the dew point temperature in the space. Supplementary air-conditioning system is required: for the removal of the latent load (moisture removal) and fresh air In dry regions, radiant system can work independently for most time of the year (except during monsoon time)

Application – Commercial Area – office spaces, schools, and few applications in hotels. – Residential –in homes, in areas where humidity is less. – Industry- Capillary tubes maybe used for an industrial application, as well as a fire suppression system – Hospitals and Laboratories – Radiant cooling can be effective to maintain aseptic environment in hospitals and laboratories. It provides a silent, draft-free, thermally stable environment for sedentary pateints.

Case Study - 1 Infosys, Hyderabad Campus Infosys, constructed – 1st radiant cooled commercial building in India in its Hyderabad campus. Total built up area - 24,000 sqm., Significant feature - split into 2 identical halves – one with conventional air conditioning (high efficiency and surpassing ASHRAE standards by about 30%) and the other with radiant cooling. Radiant Cooling System installed at Infosys, Hyderabad campus Source: First Radiant Cooled Building in India – Critical Analysis of Energy, comfort and cost - Guruprakash Sastry, Senior Manager – Green Initiatives, Infosys

Performance MetricsConventional Central ACRadiant Cooled Air conditioning Energy Index 38.7 kWh/sqm25.7 kWh/sqm Percentage energy saving33% Average Chiller plant Efficiency 0.6 kW/TR0.45 kW/TR Cost incurred per sqm (Rs)3,3273,302 Savings Achieved Case Study - 1

Teaching Aids Technical References Radiant Cooling Design Manual: efs_radiantcooling.pdf?tracked=true efs_radiantcooling.pdf?tracked=true Chapter 6 of the ASHRAE Handbook on HVAC Systems and Equipment (2000) is dedicated to the design and performance of radiant heating and cooling systems.

Contact: Vivek Gilani Managing Director, cBalance Solutions Hub Programme Director, Fairconditioning (India) Philippe DeRougemont Co-Founder, noe21 Programme Director, Fairconditioning (Switzerland)