Limbaja Energy

Cooling Tower Study

Cooling Tower Study

Overview

Cooling towers represent largest reuse of water in industrial and commercial applications. Cooling towers offers the means to remove heat from air conditioning systems and industrial processes generating excess heat. Cooling towers are normally designed for maximum process load and worst ambient conditions. Optimizing operation and effective maintenance of cooling towers systems offer facility and process managers significant savings in energy and water consumption. As result saving potential of about 20-25% can be achieved by optimizing excess capacities of pumps and fans catering to under loaded process.

Most cooling towers develop significant draft. Drift eliminator at the top of tower prevent water from being blown off or sucked out of tower. This type of water loss is called drift loss or windage loss. Makeup water is added to replenish the water lost by evaporation or blow-down.

Liquid/Gas (L/G) ratio, of a cooling tower is the ratio between the water and the air mass flow rates. Against design values, seasonal variations require adjustment and tuning of water and air flow rates to get the best cooling tower effectiveness through measures like water box loading changes, blade angle adjustments.

Scope of Work

Measurement of power parameters for cooling tower fans, water flow rate, air flow rate, dry bulb temperature (DBT) wet bulb temperature (WBT) sump temperature, relative humidity etc.
Measurement of Air flow rate of the cooling tower fan
Heat Load Calculation of the Cooling Tower
Estimation & evaluation of cooling tower performance (range, approach and effectiveness) and comparing it with designed data.
Calculations of Evaporation loss of Cooling Tower
Blowdown loss and Cycles of Concentration of the Cooling Tower
L/G Ratio of Cooling Tower

Case Study

Energy Conservation Measures : Stop the Hotwell Circulation Pump by Eliminating the Hotwell Section

    Observation

    During the energy Audit, we observed that Hot Press Return Cooling Water pour to the Hotwell Section.
    After Hotwell section pump Circulate the water to the Cold well Section.
    During the Energy Audit we observed that Cooling Cycle is 8 min to 9 Min only.

    Suggestion

    Stop the Hotwell Circulation Pump.
    Remove the Hotwell Section and Merge with Cold Well Section.
    Match the bottom level of Hotwell Section with Coldwell Section.

    Data

    SNDescriptionUnitData
    1Hot Well Circulation Pump 1 PowerkW5.551
    2Hot Well Circulation Pump 1 PowerkW5.103
    3Hot Well Circulation Pump 1 PowerkW5.056
    4Total Power ConsumptionkW15.709
    5Total Running DayDay300.00
    6Electrical Unit CostRs/ kWh8.30
    7Annual Power Saving PossiblekWh113105
    8Annual Saving in Monetary TermsRs/-938776
    9Investment of Merge Hotwell and Cold Well SectionRs/-100000
    10Simple Payback PeriodMonth1.28

    Existing Circulation of Water at Cooling Tower

    Existing Circulation of Water at Cooling Tower Diagram

    Existing Circulation of Water at Cooling Tower

    Suggested Cooling Tower Water Circulation

    Suggested Cooling Tower Water Circulation Diagram

    Suggested Cooling Tower Water Circulation

    Energy Saving Opportunities in Cooling Tower

    Follow manufacturer's recommended clearances around cooling towers and relocate or modify structures that interfere with the air intake or exhaust.
    Optimise cooling tower fan blade angle on a seasonal and/or load basis.
    Correct excessive and/or uneven fan blade tip clearance and poor fan balance.
    On old counter-flow cooling towers, replace old spray type nozzles with new square spray ABS practically non-clogging nozzles.
    Replace splash bars with self-extinguishing PVC cellular film fill.
    Install new nozzles to obtain a more uniform water pattern
    Periodically clean plugged cooling tower distribution nozzles.
    Balance flow to cooling tower hot water basins.
    Cover hot water basins to minimise algae growth that contributes to fouling.
    Optimise blow down flow rate, as per COC limit.
    Replace slat type drift eliminators with low pressure drop, self-extinguishing, PVC cellular units.
    Restrict flows through large loads to design values.

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