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Water Source Application & Competitor Comparison

Water Source Application & Competitor Comparison. Content. Water Source Product Selection Piping Sizing Water Cooler Competitor Comparison. Water Source Product Selection. Selection Criteria?. 1. Capacity required, Total Cooling (TC), Sensible Cooling (SC).

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Water Source Application & Competitor Comparison

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  1. Water Source Application & Competitor Comparison

  2. Content • Water Source Product Selection • Piping Sizing • Water Cooler • Competitor Comparison

  3. Water Source Product Selection Selection Criteria? 1. Capacity required, Total Cooling (TC), Sensible Cooling (SC) 2. Entering Air Temperature, DB/ WB 3. Entering/ Leaving Water Temperature, EWT/ LWT 4. Airflow required, CFM 5. Static pressure, Ps 5. Water Flowrate, l/s

  4. Manual Selection & Calculation • Entering Air Temperature, • Entering Dry Bulb, EDB • Entering Wet Bulb, EWB Tip: DB changes while WB remains will not affect the TC. SC2(kW)=SC1(kW)+ [1.23*(l/s)*(1-BPF)*(EDB2-EDB1)/1000] Example: if TC =3.52kW and SC=2.78kW at EDB =27C, EWB=19C. Calculate the TC and SC when EAT is as following; EDB = 30C, EWB = 19C Assuming air flow rate = 180 l/s, BPF=0.06, Water flowrate = 1.25m3/hr

  5. Manual Selection & Calculation TC = 3.52kW and SC=2.78kW EDB =27C, EWB = 19C EDB = 30C, EWB = 19C Since WB1 = WB2, then TC1 = TC2 = 3.52kW, and SC2=SC1+ [1.23*(l/s)*(1-BPF)*(EDB2-EDB1)/1000] = 2.78+[1.23*180*(1-0.06)*(30-27)/1000] = 3.40kW

  6. Selection & Calculation by Selection Software Download selection software from e-biz. • Select model type • Select indoor if split type was chosen • Chose the fan speed • Key in the water flow • Key in the on coil temperature and EWT temperature • Key in the designed capacity to fulfill the building heating/cooling load requirement. • Key in the capacity tolerance (%) • Click “Calculate”

  7. Selection & Calculation by Selection Software Selection Result 9. Select the model closest to the capacity requirement

  8. Example of Piping Sizing 1. Determine System Water Flow Rate • DON’T sum up directly the total nominal water flow of each WSHP unit. • Total System design flow rate is determined by the performance of the water cooler, where most of them are evaporative type and is very much dependent on the entering air wet bulb temperature. • Lower flow rate are preferred in areas with lower wet bulb temperatures. In more humid areas, a higher water flow rate will supply a higher water temperature to water source units, but with a lower differential.

  9. Example of Piping Sizing 2. Determine WSHP unit flow rate • Total Cooling load must be known. • Diversity Effect must be considered. This is to prevent over sizing water cooler Diversity Factor = Block Load / Σ(Peak Load) • Recommended diversity factor; • 85% for system up to 40 tons • 80% for system between 40 and 60 tons • 75% for system greater than 60 tons • System diversity will only affect the range of the water cooler.

  10. Example of Piping Sizing 2. Determine WSHP unit flow rate (Cont…) Range of Water Cooler, Rs = Twi – Two Where; Twi = entering water temperature Two = leaving water temperature • By using diversity factor, D, we can then calculate the avarage range of the water source units, Rp Rs = D * Rp • Where typical value of range are between 5C to 8C or equally 9F to 14.4F.

  11. Example of Piping Sizing 3. Determine individual unit peak cooling load • By assuming 30% of heat rejection ratio, Total heat rejection, Qh Qh = 1.3 *D* Qc Qh = mw * Cp * (Twi – T wo) Where mw = mass flow rate of water Cp = water specific heat Total cooling peak load, Qc • By replacing with known constants, we will get these familiar equations; Qh = 500 gpm (Twi – T wo)

  12. Example of Piping Sizing 3. Determine individual unit peak cooling load (Cont…) • By having water cooler range, Rs in the equation; Qh = 500 * gpm * Rs • By having total peak cooling load, Qc in the equation; 1.3 *D* Qc = 500 * gpm * Rs • Thus the individual unit peak cooling load, qc 1.3 * qc = 500 * gpm * Rp

  13. Example of Piping Sizing Example: • A water loop system consists of 30 units of water source heat pump units with a combined total peak loading of 450,000btu/hr. the system is served by a centrifugal water pump. A closed loop water cooler is used to give a leaving water temperature of 30C. the ambient air wet bulb temperature is 25C. • Determine the required total system water flow rate. • From the given table, at 25C wet bulb temperature, the water flow rate is 2.36 gpm/ton. • Therefore, the total system water flow rate is 2.36 gpm/ton * (450000/12000)ton = 88.5 gpm. • Calculate the average range of the water source units • The system range is first calculated; • Rs = 1.3 * D * Qc / gpm / 500 = 1.3 * 0.85 * 450,000 / 88.5 / 500 = 11.24F or 6.24F • Rp = Rs / D = 13.22F or 7.35F • If one of the water source units has been designed to give a cooling capacity of 11,000btu/hr, calculate the water flow rate required. • Rp = 1.3 * qc / gpm / 500  13.22 = 1.3 * 11000 /gpm/500 ; gpm = 2.16gpm • Recalculate if there is no diversity factor is applied. • If D = 1, and maintaining the flow rate, Rp = Rs / D = 13.22F or 7.35F

  14. Example of Piping Sizing 4. Piping Sizing • Important to ensure the selected water pump is sufficient to deliver the required water flow rate. • To do this calculation, it is important that a detailed drawing layout of all components in the system is available. • The layout should give dimensional lengths of the piping network. • Location of water cooler, pumps and boiler must be identified. • All fittings and accessories used in the piping installation should be clearly identified. • Study the pipe circuit layout and do preliminary check if the circuits are balanced. Re-arrange if necessary. Use balancing valves only if it is not possible to have balanced circuits. • Size the pipes by using the pipe chart. The water velocity should be in the range of 2 – 9 fps, with a recommended max friction loss of 10 ft of water per 100 ft.

  15. Example of Piping Sizing 4. Piping Sizing (Cont…) • Calculate equivalent pipe length. Include the losses for all the valves and fittings used. Calculate the total pipe friction loss by using the friction loss value from the pipe chart. Add this with the pressure drop in heat exchangers, water cooler and boiler. • Select a pump which will match these total system water flow rate and total head pressure.

  16. Example of Piping Sizing Example: The water source units which serve the main building has a total installed cooling capacity of 560,000 btu/hr (peak load). There a altogether 40 sets, with 10 sets for each of the four floors (1st floor to 4th floor). The water source units have been selected based upon the following conditions: Entering air = 25C DB / 18C WB Entering water = 32C All the units are connected to an evaporative water cooler located on top of an adjoining service building outside of the main building. The outside air wet bulb temperature is at 24C

  17. Example of Piping Sizing Example: (Cont..) • Calculate the total system water flow rate. • Total installed capacity = 560,000 btu/hr (46.67 tons) • Therefore, the total system water flow rate @ 24C wet bulb is • 2.19 gpm/ton * 46.67 tons = 102.2 gpm. • Calculate the range (Rs) of water cooler • For 46.67 tons, use diversity factor of 0.80. • Rs = 1.3 * D * Qc / gpm / 500 = 1.3 * 0.80 * 560000 / 102.2 / 500 = 11.40F or 6.3C. • Calculate the range (Rp) of water source units. • Rp = Rs / 0.80 = 11.40/0.80 = 14.25F or 7.9C.

  18. Example of Piping Sizing Example: (Cont..) • The unit on the 4th floor have been sized to give the following peak loads; • By using equation 1.3 * qc = 500 * gpm* Rp, we can then work out the flow rate through each of these units. Let assume that the total system water flow rate is distributed to all the four floors of the main building in this manner.

  19. Example of Piping Sizing Example: (Cont..) • With this, we can no look into the pipe sizing all the way up to 4th floor. Focus is given to determine the route of least favourable which will give the max friction loss to the water pump. i.e. all the way to unit q. • Reference is then made to pipe chart to determine a suitable pipe size.

  20. Example of Piping Sizing Example: (Cont..) • Each of the WSHP has fittings as shown in the diagram below: The water pump has been installed in this manner:

  21. Example of Piping Sizing Example: (Cont..) Detail of water pipe connection to the evaporative water cooler is as shown below:

  22. Example of Piping Sizing Example: (Cont..) 7. With all these fittings details and pipe lengths, we can now calculate the pipe friction loss from the water cooler to point q. This is as demonstrated in this summary table.

  23. Example of Piping Sizing Example: (Cont..)

  24. Water Cooler Type of Water Cooler Evaporation of Water to cool the condenser 1. Closed Circuit Cooling Tower 2. Open type cooling tower with heat exchanger Air Cooled 3. Dry Cooler

  25. Water Cooler Terminology Open Cooling Tower An evaporative equipment that exposes water directly to the cooling atmosphere, thereby transferring the heat load directly into the air.

  26. Water Cooler Terminology Closed Circuit Cooling Tower An evaporative equipment that contains two separate fluid circuits. The first is an external circuit where water is exposed to the atmosphere as it cascades over the tubes of a coil bundle. The second is an internal circuit in which the fluid to be cooled circulates inside the tubes of the coil bundle.

  27. Water Cooler Terminology Induced Draft Type of mechanical draft tower in which one or more fans are located at the air outlet to induce air through the air inlets Forced Draft Type of mechanical draft tower in which one or more fans are located at the air inlet to force air into the tower.

  28. Water Cooler Terminology Counter Flow In a counter flow cooling tower, the air enters at the base of the tower, flows upwards and interfaces counter currently with the falling hot water. Cross Flow In a cross flow cooling tower, the air flows horizontally through the cooling tower and interfaces perpendicularly with the falling hot water.

  29. Water Cooler Terminology Approach The diff between the water temperature leaving the cooing tower and the wet bulb temperature of the cooling air (atmosphere)

  30. Water Cooler Terminology Evaporation Loss Loss of water from the cooling tower as a result of evaporation of the circulating water; %E = [Range(C) * Circulating flow rate (kg/hr) * 100]/600 Where range = the diff between the leaving and entering water temperatures of the cooling tower.

  31. Water Cooler Terminology Drift Loss Loss of water from the cooling tower as a result of carry over of minute water droplets scattered about as drifted by the fan. Blow Down Volume The amount of water discharge from the cooling tower to prevent concentration build up of dissolved minerals which may cause the formation of algae or scale.

  32. Water Cooler Terminology Make Up Water (M%) The amount of water that is required to maintain the water level in the cooling tower basin. M = E + C + B

  33. Water Cooler “Hybrid” System Closed Circuit and Open Circuit Tower

  34. Water Cooler Water Distribution System 1. Gravity Distribution • Open Basins • Large Orifice, 360 Nozzles • Easily accessed for maintenance • Basin water level used to balance flow 2. Spray Distribution • Pressurized systems • Large Orifice, 180 directional Nozzles • spray header and branches

  35. Water Cooler Air Moving 1. Axial Fan 2. Centrifugal Fan • >80% is used in HVAC system • High volume, low static pressure • High efficiency • Low energy consumption • Improve sound ratings • High volume, high static pressure • High energy consumption • Quiet operation • Tight layout requirement • Example, 1500 GPM, 95F EWT. 85F LWT, 78F EWB - Counter flow centrifugal fan unit requires 60 HP - Cross flow axial fan unit requires 30 HP * Axial fan requires less HP than centrifugal fan*

  36. Water Cooler Cooling Tower Equipment Layout • Prevent warm air or drift from being introduced into fresh air intakes or from being carried over populated areas • Consider the potential for plume • Note the direction of the prevailing winds • Ensure adequate supply of fresh air to the air intakes • Provide adequate space for piping and proper servicing and maintenance • Top of the unit discharge must be at least level with the adjacent wall

  37. Water Cooler Layout Example • Adjacent to a wall or building • In an enclosure • Adjacent t a louvered or slotted wall

  38. Water Cooler Layout Example • Correct cooling tower installation when located adjacent to a building or wall • Maximum air velocity should no t exceed 300 FPM or 1.5m/s • Air entry envelope consists of top and two sides • Based o 125,900 CFM, an inlet height of 10 feet and an air inlet length of 12 feet, the distance to the wall is ; • 125,900/2 = (10+10+12)D*300 • D = 6.56 feet

  39. Water Cooler Layout Example • When cooling towers are positioned with air inlets facing each other, the distance between cooling towers is 2D • If 125,900 CFM, an inlet height of 10 feet and an air inlet length of 12 feet, the distance to the wall is ; • 125,900*2/2 = (10+10+12)D*300 • D = 13.11 feet

  40. Water Cooler Layout Example • Maximum air velocity should not exceed 400 FPM • Center of the cooling tower within the enclosure for uniform air flow to the air inlets • If 125,900 CFM, enclosure size is 30ft * 20ft ; • 125,900 = 2*D*20*400 • D = 7.87 feet

  41. Water Cooler Layout Example • Louver must provide at least 50% free area • Louver air velocity should not exceed 600 FPM • Maintain at least 3 ft between the tower air inlets and the louvered wall.

  42. Water Cooler Maintenance – Who needs this?

  43. Water Cooler Maintenance Maintenance and water treatment are the most neglected regimens of cooling tower operation, and cooing towers are generally the most neglected components in the mechanical system WHY??? • Remotely located & difficult to access • Limited maintenance resources • People, Training & budgets.

  44. Water Cooler Maintenance Review major cooling tower system sand their appropriate maintenance regimens: • Circulating Water • Fan & Drive • Fin & Coil • Air Entry Louvers • Drift Eliminators

  45. Water Cooler Maintenance Reputable manufacturers provide maintenance instructions and check sheets. It is best to follow the manufacturer’s recommendations! ASHRAE Handbook also provides a good general guide.

  46. Water Cooler Circulating Water System Types Gravity Flow Water Distribution System Cross flow tower operation View of water distribution box

  47. Water Cooler Circulating Water System Types Pressurized Flow Water Distribution System Closed Circuit Tower Operation View of Pressurized Distribution System & Nozzles

  48. Water Cooler Circulating Water System Types • Spray nozzles & water distribution boxes need to be inspected & cleaned • After start up and • Monthly thereafter • Regular inspection allows quick treatment and control of corrosion and mechanical failures.

  49. Water Cooler Circulating Water System Types • Clogged distribution nozzles cause: • Reduced or mal-distributed water flow = capacity reduction • HE surface scaling/ fouling = capacity reduction • Overflowing distribution boxes = water & chemical loss • Excessive drift = water & chemical loss • Fan motor over-amping (forced draft) = reduced motor life

  50. Water Cooler Circulating Water System Types • Suction Strainers: • Designed to protect pump & nozzles • Inspect & clean weekly • Operating environments laden with airborne fibrous material ( agricultural, paper, textile processing demand more frequent strainer cleaning)

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