1. Adapted control systems for house service connection stations of huge performance – domestic hot water supply based on continuous flow system Faculty of Mechanical Engineering Institute of Power Engineering, Second Euroheat & Power RTD Workshop Brussels, 2-3 February 2006 Dipl.-Ing. Norbert Wünsche, Dr.-Ing. Karin Rühling 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) Professorship of Energy System Engineering and Heat Economy

2. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 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

3. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 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

4. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 4 Tested basic configurations on DHW side Two-stage principle – during tapping t return , as no mixing circulation/cold DW primary storage of heating water supply return DHW DW circulation

5. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 5 Basic configurations for charging the primary storage Control system without auxiliary power demand Thermo mechanical valve Three-point control Motor control valve direct charging Two-point control Motor control valve Three-point control Motor control valve indirect charging Adjusted charging temperature

6. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 6 Choice of the pump

7. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 7 Set-up of the laboratory test facility temp. HX inlet temp. DHW with sensor head trans- mitter temp. circ. return SIKA flow control switchtemp. DW nonreturn valve temp. HX outlet  Single-stage realisation  Q th, design = f(t storage ) = 100 …150 kW  Switching the mixing valve via flow control switch 0.. 12 l/min  t HX,in =65 °C > 12 l/min  t HX,in = t storage  Control pump Grundfos TPE 25-90R (smallest available)  Plate HX SWEP B28 x 30  Rudert DW-storage 200 l

8. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 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

9. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 9 Selected results of the laboratory tests with 72 °C storage temperature Load profile Step curve Load profile Jump function

10. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 10 Selected results of the laboratory tests Load function / storage temperature Maximum values Minimum values average positive deviation average negative deviation Step curve 72 °C+2,2 K-3,6 K+0,3 K-1,2 K Jump function 72 °C+5,5 K-3,6 K+0,7 K-1,1 K Step curve 80 °C+2,1 K-1,9 K+0,2 K-0,4 K Jump function 80 °C+6,5 K-5,7 K+0,5 K-0,7 K

11. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 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

12. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 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)

13. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 13 Field test - Selected results – Daily average values Remarkable higher control stability in the two-stage realisation (± 2K)

14. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 14 Field test - Selected results – Daily course; two-stage

15. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 15 Field test - Selected results – Peak demand; two-stage

16. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 16 Field test - Selected results – Frequency distribution DHW demand  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 frequency distribution flow rate of area-equivalent rectangle: 0,134 m 3 /h time in % flow rate in m 3 /h

17. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 17 Field test - Selected results – Daily course; single-stage

18. Brussels, 2 February 2006Huge DHW supply based on continuous flow system Wünsche/Rühling Slide 18 Field test - Selected results – Peak demand; single-stage