Second Euroheat & Power RTD Workshop Brussels, 2-3 February 2006

1. Faculty of Mechanical Engineering Institute of Power Engineering, Professorship of Energy System Engineering and Heat Economy Adapted control systems for house service connection stations of huge performance – domestic hot water supply based on continuous flow system Dipl.-Ing. NorbertWünsche,Dr.-Ing. KarinRühling TU Dresden, Institut of Power Engineering This presentation is based on a research project financially supported by the German Federal Ministry of Economy within the PROgramm “INNOvationskompetenz mittelständischer Unternehmen” (KF 0100804KMH3) Second Euroheat & Power RTD Workshop Brussels, 2-3 February 2006

2. MOTIVATION Domestic hot water supply in the range of 100 kW to 1 MW • Standard installations temporary mostly as storage systems favourable conditions for growth of Legionella •  Cause of high quality standards (TrinkwV, DVGW W 551) special solutions with considerable high efforts necessary Storage charging system Storage of DHW Storage system Storage of DHW Huge DHW supply based on continuous flow system Wünsche/Rühling

3. OBJEKTIVE Check, if continuous flow system can be applied • simple hydraulic circuit • primary storage for heating water • domestic hot water temperature control system based on speed control of electronic pumps Continuous flow system with primary storage Storage of heating water Continuous flow system Without storage Huge DHW supply based on continuous flow system Wünsche/Rühling

4. Tested basic configurations on DHW side DHW supply primary storage of heating water circulation return DW Two-stage principle – during tapping treturn, as no mixing circulation/cold DW Huge DHW supply based on continuous flow system Wünsche/Rühling

5. Basic configurations for charging the primary storage Control system without auxiliary power demand Thermo mechanical valve Two-point control Motor control valve Three-point control Motor control valve indirect charging Three-point control Motor control valve direct charging Adjusted charging temperature Huge DHW supply based on continuous flow system Wünsche/Rühling

6. Choice of the pump Huge DHW supply based on continuous flow system Wünsche/Rühling

7. Set-up of the laboratory test facility temp. HX inlet • Single-stage realisation • Qth, design = f(tstorage) = 100 …150 kW • Switching the mixing valve via flow control switch 0 .. 12 l/min  tHX,in=65 °C > 12 l/min  tHX,in= tstorage • Control pump Grundfos TPE 25-90R (smallest available) • Plate HX SWEP B28 x 30 • Rudert DW-storage 200 l temp. DHW with sensor head trans-mitter temp. circ. return temp. HX outlet nonreturn valve SIKA flow control switch temp. DW Huge DHW supply based on continuous flow system Wünsche/Rühling

8. Key aspects of the laboratory tests • Test of different hydraulic circuits • Measuring the time constants of different temperature sensors • Placement of DW-temperature sensor in heat exchanger • Examination of the control range of the electronic pump • Dimensioning the admix-quantity • Choice of proper mixing valve • Choice of appropriate flow control switch • Optimisation of pump control parameters Huge DHW supply based on continuous flow system Wünsche/Rühling

9. Selected results of the laboratory tests with 72 °C storage temperature Load profile Step curve Load profile Jump function Huge DHW supply based on continuous flow system Wünsche/Rühling

10. Selected results of the laboratory tests Huge DHW supply based on continuous flow system Wünsche/Rühling

11. Field test – Objectives • Prove under praxis conditions • uninterrupted service, • dimensioning of performance, • stability of control, • effectiveness of primary storage (coverage of peak demands) as well as • low return flow temperatures and thus • function of complete system Single-stage realisation Huge DHW supply based on continuous flow system Wünsche/Rühling

12. Field test – Conditions of application • For 53 living units • two-stage DW-heating • first operation period single-stage and later two-stage operation • mixing loop as independent temperature control circuit • no cold water flow sensor • data logging 11 temperature sensors 3 flow rate sensors average value logging (2 or 5 s–pulse) • 8 weeks save and convenient supply of tenants • V´DHW,max = 2,95 m³/h (Comparison: DIN 4708 4,8 m³/h) Huge DHW supply based on continuous flow system Wünsche/Rühling

13. Field test - Selected results – Daily average values Remarkable higher control stability in the two-stage realisation (± 2K) Huge DHW supply based on continuous flow system Wünsche/Rühling

14. Field test - Selected results – Daily course; two-stage Huge DHW supply based on continuous flow system Wünsche/Rühling

15. Field test - Selected results – Peak demand; two-stage Huge DHW supply based on continuous flow system Wünsche/Rühling

16. Field test - Selected results – Frequency distribution DHW demand flow rate in m3/h frequency distribution flow rate of area-equivalent rectangle: 0,134 m3/h time in % • DHW-demand only 32 % of the time • only during 10 % of the time demand > 0,5 m³/h • dimensioning of primary storage = f (circulation demand, operation parameter of heat exchanger, mixing loop, storage temperature ..)  program for dimensioning Huge DHW supply based on continuous flow system Wünsche/Rühling