WINTER INTERNSHIP 2021 | SESSION 7 | HVAC Design & Drafting | Ducting & Water Piping | #hvac #mep

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Air flow problems have plagued the HVAC industry for years. No matter how much money
you spend on a high-quality HVAC system, the equipment won’t work at its best without
properly designed and installed ductwork. Ducts that are not well designed result in
discomfort, high energy costs, bad air quality, and increased noise levels.
A well-designed ductwork system should deliver maximum interior comfort at the lowest
operating cost while also preserving indoor air quality. The chief requirements of an air
conditioning duct system are:
1. It should convey specified rates of air flow to prescribed locations.
2. It should be economical in combined initial cost, fan operating cost and cost of
building space.
3. It should not transmit or generate objectionable noise.
A primary issue is the tradeoff between the initial cost of the duct system and the energy cost
of the air distribution system. Larger ducts require a larger initial investment, but result in
lower fan energy costs over the life of the system. Other issues include space restrictions,
noise level, capacity for expansion, appearance, etc.
This course will discuss the basic fundamentals and principles of air conditioning duct design
and layout.

Chilled water piping basics
1. CHILLED WATER SYSTEM

CHW SYSTEM COMPONENTS 1. CHILLER –AIR COOLED , WATER COOLED 2. CHW PIPING 3. PUMPS 4. COOLING TOWER (FOR WATER COOLED) 5. AHUS

CHILLER BASICS 1. Chilled water flows thru the evaporator .The evaporator is a heat exchanger 2. Chiller compressor may be centrifugal, scroll, screw or reciprocating 3. The condenser may air cooled or water cooled 4. There can be multiple chillers in a chw plant

FLOW CALCULATION 1. Common design condition is supply water 44 F ,return water 54 F temperature difference 10

FLOW VELOCITY 1. Too low flow rate affects chiller efficiency 2. Too high flow rate cause vibration noise & tube erosion 3. The recommended flow rate is between 3- 12 fps

CHILLER EER 1. Chiller is the largest single point electriccity user in a building 2. EER = TR * 12/kw input 3. The recommended flow rate is between 3- 12 fps 4. Chillers rarely work in full load condition (2 %) hence NPLV is very important

EXPANSION TANK 1. Essential to manage the thermal expansion 2. Can be open type or closed type 3. Open tanks must be located above the highest point 4. Air water interface or diaphragm tank can be located anywhere in the system 5. The lower the pressure in the tank the smaller it is

8. PIPING BASICS 1. Once through & re circulating 2. Open & closed type 3. Friction loss in pipe will depend up on  Velocity  Interior surface roughness  Diameter  length 4. For long run pipes expansion joints are provided 5. the pressure in the tank the smaller it is 6. The chw Pipes should be insulated

9. PIPING BASICS 1. Piping is usually steel, copper or plastic 2. Usually closed loop 3. Cooling tower piping is open loop 4. Generally the static pressure is less than 150 psi 5. If the system is above 150 psi static intermediate HE or chw systems are used
 PIPING VALVES 1. 2 way or 3 way valve to direct/by pass the flow 2. Balancing valve to control the flow 3. Gate valves for isolation 4. Globe valves for throttling 5. Butterfly valves – Isolation, throttling 6. Strainers- For filtration 7. Flexible bellows –Vibration arresting 8. NRV-at pump discharge 9. Pressure & temperature gauges

11. BALANCING VALVE

12. TRIPLE DUTY VALVE

13. GATE VALVE

14. BUTTERFLY VALVE

15. STRAINER VALVE

16. FLEXIBLE BELLOW

17. 2 WAY & 3 WAY VALVE

18.  BALL VALVE

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