Efficient Low Temperature Heating Systems By: Arefeh Hesaraki Supervisor: Prof. Sture Holmberg KTH Royal Institute of Technology School of Architecture and Built Environment, Division of Fluid and Climate Technology
Agenda 1) Background Low Temperature Heating Systems Principle of Ventilation Radiator Advantages of Ventilation Radiator 2) Case Study (Invistigation of energy consumption in a building equiped with low temperature heating system) Energy Calculation Simulation with IDA ICE Comparision 3) Future Work 4) Conclusion
Hydronic Heating Systems
Low Temperature Heating Systems Supply flow temperature: 45 C The lower the temperature, the lower the energy consumption for heat production Potential of using low temperature heating sources (sun, ground, waste heat...) Enviromentally friendly system
Low Temperature Heating Systems More thermal efficient than high temperature heating system(general rule of thumb: thermal efficiency of heat pump improves by 1-2% for every degree reduction in supply water temperature) Results from licentiate thesis by Adanan Ploskic Well known: Floor, wall, ceiling heating, Our project: ventilation radiator
Principle of Ventilation Radiator Preheated air-inflow a) b) d) a) Vent grill on the building wall, b) channel through wall, c) injector or inlet (with or without mixing of cold supply air with room air) d) traditional radiator c) Cold outdoor air (8-10 l/s) Driving force: buoyancy forces and pressure differences between outdoors and indoors due to exhaust ventilation fan
Principle of Forced Convection Blowing on food External flow water We resort to forced convection whenever we need to increase the rate of heat transfer air Internal flow Internal flow of water in a pipe and the external flow of air over the same pipe
Advantages of Ventilation Radiator Enhance the convective heat transfer 1) The higher air velocity, the higher forced convection, the higher heat output 2) The greater the temperature difference between the cold incoming air and the heating unit, the higher thermal exchange to the air-inflow (It is therefore less important to adjust the water temperature level or the mass flow rate in the radiator circuit to change indoor temperatures. The ventilation radiator automatically regulates its own heat output) Results from doctoral thesis by Jonn Are Myhren Results from licentiate thesis by Adanan Ploskic
Advantages of Ventilation Radiator Laboratory measurements show Traditional radiator Ventilation radiator Ventilation radiator gives double heat output than traditional radiator The same heat output in working with 35 C of supply water temperature with supply water temperature of 55 C in traditional radiator 10 l/s of incoming ventilation air at three temperature levels, water mass flow of 0.01kg/s Results from doctoral thesis by Jonn Are Myhren
Advantages of Ventilation Radiator Preheat the supply air inside the radiator with mixing of cold supply air with room air without mixing of cold supply air with room air Results from doctoral thesis by Jonn Are Myhren
Case Study Invistigation of energy consumption in a building equiped with low temperature heating systems Location Type Heating source Heating Systems Area Construction company Stockholm-Sweden Semi-Detached House Exhust heat pump Ventilation radiators in second and third floor, under-floor heating in first floor 160 m2 NCC
Heating Demand (kwh) Energy Calculation 2500 2000 Transmission Losses Q trans = U j A j + ψ i l i [W ] 1500 Ventilation Losses Q vent = ρ c p q vent + ρ c p q leak [W ] 1000 500 0 Passive Heat People Solar Hot water Electricity Active Heating Demand E active = E trans+vent E passive Total Heating Demand: 57.6 (kwh/m2)
Simulation Using IDA ICE 4.2 One zone for the whole parts The same size and location of windows and doors Use the same heating system
Heating Demand (kwh) Simulation Results 2000 1800 1600 1400 1200 1000 800 600 400 200 0 Total Heating Demand: 61.7 (kwh/m2)
Comparision 70.0 60.0 50.0 40.0 30.0 20.0 IDA Calculation Manual Calculation NCC Calculation by Enorm 2004 10.0 0.0 Heating Demand (kwh/m2)
Disscusion Swedish building regulations IDA Calculation 61.7 kwh/m2 Enorm Calculation by NCC 57 kwh/m2 Manual Calculation 57.6 kwh/m2
Future Work Site measurements of energy consumption Questionear of thermal comfort answerd by occupants More detaile model, one zone for each part of the building Investigation of combining the low temperature heating systems with solar energy as a heating source
Conclusion According to the previous study ventilation radiator systems may both save energy and create comfortable indoor climate. The heat output of ventilation radiator is approximately two times higher than conventional heating system. The low-temperature heating systems are more sustainable and more environmentally friendly than high-temperature heating systems
Thank you for your attention Arefeh.Hesaraki@byv.kth.se