Estimation of Air Handling Units Condensate Recovery in the Medical Campus Buildings at the University of Alabama at Birmingham

Presented by Atul Kajale1, Robert W. Peters1, Matthew Winslett2

1Civil, Construction, and Environmental Engineering University of Alabama at Birmingham2Facilities Management Department University of Alabama at Birmingham

Presented at Alabama Water Resources Conference 2012

Orange Beach, AL September 6th, 2012

1.Introduction

2.Problem Statement and Objectives

3.Literature Review

4.Methodology

5.Results and Discussion

Overview

Air Handling Units (AHUs) Part of Heating, Ventilating, and Air Conditioning (HVAC) system Used in commercial, industrial, and institutional buildings because it can handle large volumes of air During cooling season (summer), chilled water is used for cooling the hot outside air

Condensate Recovery Collection and reuse of condensate formed inside the AHU Save money by reusing condensate water as make-up water in the chilled water plant, irrigation, toilet flushing (water conservation technique), etc. Achieve both water and energy conservation goals

Introduction

Problem Statement Currently, there is no accurate method to predict the amount of condensate amount from Air Handling Units (AHUs). The previous models typically underestimate (~30%) the condensate volumes and hence there is need for improvement in the estimation method. Due to this, there is error in estimation of the payback period so it is difficult to evaluate the feasibility of a Condensate Collection System No previous research has been performed for the Birmingham, Alabama location

Problem StatementHypotheses Null Hypothesis: The amount of condensate

water predicted using the current study and the previous studies are the same.

Alternate Hypothesis: The amount of condensate water predicted using the current study and the previous studies are not the same.

Questions to be addressed: What is the interaction of various parameters on

condensate recovery? Is the CCS feasible for the Birmingham location? What is the quality of condensate water? How much make-up water is required and

supplied?

Problem Statement To develop a more accurate method for predicting

the condensate recovery quantity from AHU condensation;

To determine the factors affecting the condensate production rate (including interaction terms);

To analyze the quality of the condensate water and its application for on-campus activities; and

To determine resulting water savings, payback period, Life Cost Assessment (LCA) and Life Cycle Cost (LCC) analysis

Intensity of Drought in Southeastern U.S., August 2007

Introduction (cont’d)

Figure 1. Intensity of Drought in Southeastern U.S., August 2007(Source: U.S. Drought Monitor, University of Nebraska, Lincoln 2011)

Water Scarcity and Drought Condition

Figure 2. Intensity of Drought in Alabama in Year 2012(Source: U.S. Drought Monitor, University of Nebraska, Lincoln 2012)

Feb. 14, 2012 March 20, 2012 May 29, 2012 July 24, 2012

Introduction (cont’d)

Water Scarcity and Drought Condition

Figure 3. Water Supply Sustainability of Projected Demand in Year 2050 under Changing Climatic Scenario

(Source: Sujit Roy, TetraTech Inc., 2010)

Introduction (cont’d)

Future water availability is based on:• current water usage data

at the county level, • energy usage,• population, • economic developments,

and • sixteen established

climate models.

Water Scarcity and Drought Condition

Figure 5. Effect of population on fresh water withdrawals in Alabama. (U.S. Geological Survey, 2005)

Introduction (cont’d)

Water Scarcity and Drought Condition “Drought is a natural event that does not occur in a violent burst but gradually happens; furthermore, the duration and extent of drought conditions are unknown because rainfall is unpredictable in amount, duration and location” (Office of Water Resources, ADECA, Alabama, 2004)

Social, economical, and environmental effects Slow response, and unpreparedness in mitigation Commercial, and industrial operators to lower their

water consumption There is a need to grow water conservation awareness, and a

need for more research to develop effective water conservation techniques that are unique to the local conditions of the area.

Introduction (cont’d)

Background Studies Several CCS projects have been installed in the recent past,

only 3 studies performed detailed analysis Bahrain Airport Services in the Middle East recycles 2.3

million gallons of condensate water every year for toilets flushing, washing, and landscaping.

EPA's Environmental Services Branch Laboratory in Houston, Texas, collects 832,000 gallons of water every year, project cost of $6,000,saved $20,000 over past 6 years

National Air and Radiation Environmental Laboratory (NAREL), Montgomery, Alabama installed CCS, help facility to reduce water use by 800,000 gallons annually, 65% of facility’s water use. Expected to save 1 million gallons of water annually.

Literature Review

Background Studies Formula used by Karen Guz (2005)

Formula used by Bryant and Ahmed (2008) to estimate the quantity of condensate water is stated as below:

where, CFM=volumetric air flow in cubic feet per minute ΔT= temperature difference across the chilled water cooling in °F

Literature Review

Background Studies Model developed by Lawrence et al. under this study is given

below:

where: Δώ is the difference in absolute humidity between the incoming outdoor air and the supply air leaving the unit.

The observed amount of condensate collected was 171,793 gallons, and the predicted amount was 134,021 gallons (28% lower)

Literature Review

Factors Affecting the Production of Condensate RateGeographical Location and Hot and humid weather

Literature Review

Figure 6. Condensate Collection Potential in United States. Lawrence and Perry, (2010)

Factors Affecting the Production of Condensate Rate Building use and occupancy

Typical office, classroom, retail buildings require large amounts

of outside air but part of it is always re-circulated

Hospitals, manufacturing process plants, storage buildings,

Laboratories require 100% outside air in every air exchange

The greater the volume of air supply rate, the greater the

amount of condensate generated as it depends on the relative

humidity

Literature Review

Figure 8. Schematic of the Condensate Recovery System.

Methodology

Parameters of Interest Condensate water collected Temperature, Dry bulb temperature Dew point temperature Relative humidity Air supply rate Intake air volume per exchange Area of the building served by the air handler Capacity of the air handler

Methodology

All Buildings utilize 100% outside airBuilding Name System Installation Cost Remarks

McCallum Building(MCM)

2 AHUs drains into 2 storage tanks

$25,000 McCallum and Kaul share one 500-gallon tank; started in May 2011Kaul Building (KB) 5 AHUs drains into

one 500-gallon tank$16,220

Zeigler Building(ZB)

3 AHUs drains into two storage tanks

$5,500 Zeigler and Tinsley Harrison Tower share a one 500-gallon tank; started in May 2011

Tinsley Harrison Tower (THT)

10 AHUs drain into a 500-gallon tank

$2,475

Bevill Building (BB)

6 AHUs drains into two 500-gallon tanks

$29,965 Started in August 2011

Total $79,160

Methodology

Condensate Water Collection: Kaul AHU #4 June 2012 July 2012

Results

0 10 20 30 40 50 60 70 80 90 1000

20406080

100120

f(x) = 0.989526671961935 x + 0.450278753933638R² = 0.960569583925401

Water Pumped in gallons

Wat

er a

dded

in g

allo

ns

June 2012 July 2012

Kaul #4 Water Added Water Pumped Water Added Water PumpedTotal Volume

(gallons) 17,776.03 17766.82 53,309.86 53,317.87Average Volume 45.23 45.21 71.65 71.67

Standard Deviation 9.52 8.19 27.09 27.25Maximum 90.95 95.66 116.80 116.99

0 20 40 60 80 100 120 1400

20406080

100120140

f(x) = 0.994298725850231 x + 0.41928070856541R² = 0.977217532870509

Water Pumped in gallons

Wat

er A

dded

in g

allo

ns

Condensate Water Collection: Kaul AHU #4Results

Kaul #4 Total Average Std. Dev. MaximumJune 17,776.03 45.23163 9.512099 90.94465July 53,309.86 71.65304 27.08663 116.7918

August 46,817.23 65.75454 27.97125 109.2404117,903.1

MCM #1June 27,540.39 70.04769 36.53066 142.4811July 82,795.32 111.284 43.6994 172.2053

August 78,276.2 109.9385 35.2959 167.8352188,611.9

MCM #1June 33,421.75 84.99098 34.28401 160.3069July 85,981.64 115.5667 58.57804 223.176

August 88,269.82 123.9745 46.05853 216.9447207,673.2

Condensate Water Collection: Kaul AHU #4Results

MCM Total Total Average Std Dev MaxJune 101,887.7 141.5107 158.4247 584.5533July 343,225.6 461.3247 176.394 753.8601

August 385,282.1 541.1266 237.2616 936.2425830,395.4

Zeigler THT TotalJune 93,702.56 239.0371 158.4247 584.5533July 232,296.7 325.3456 149.5222 665.0874

August 235,157.8 330.2778 237.2616 936.2425561,157.1

Effect of weather parametersResults

Model R2 Std Error P Intercept Temp Dew Humidity

June 0.82 8.72 1.72E-54 -251.968 1.13 2.88 48.82July 0.80 6.13 5.16E-39 -182.92 -0.17 4.12 -13.62Aug 0.86 10.5 6.8E-63 -355.45 1.7 3.49 70.76

Interaction of weather parameters

Model R2 Std Error P Intercept CoefficientTemp 0.11 27.65 0.019 28.55 0.47

Dew Point Temp

0.85 10.66 4.5E-298 -271.328 4.9

Humidity 0.22 24.45 0.0196 9.32 76.62

Q = f1 (Tdry), f2 (RH), f3 (Pbar), f4 (CPMair supply rate)

Q = f5(combination of Tdry , RH, Pbar , CPMair supply rate )

Q = aT+bRH+cPbar+dCPMair supply rate +error

Condensate Water Quality AnalysisResults

Preliminary water quality analysis conducted in April 2011

Impurities Concentration Concentration

Aluminum 44.7% 4.47 ppb

Iron 38% 3.8 ppb

Sulfate 9% 0.9 ppb

Zinc 3.6% 0.36 ppb

Copper, Magnesium

<2% < 0.2 ppb

Silica, Calcium <2% < 0.2 ppb

Bacteria, Fungi Positive -

DiscussionIt is expected that model developed during this study will

provide more accurate predictions of condensate volumes – less than 15% difference in predicted and observed values is expected

Over 1.4 million gallons of water is recovered in 2.5 months which is equivalent to a saving of $5900.More accurate payback period calculationsPreliminary water quality analysis suggests no treatment to water except for fungi and algaeInteraction of temperature, relative humidity, air supply rate, pressure on condensate production will be examined and a best fit equation will be developedKnowledge of the environmental performance of the project

Acknowledgement Dr. Robert W. Peters, Ph.D., P.E., Department of Civil, Construction, and Environmental Engineering at The University of Alabama at Birmingham.

Mr. Matt Winslett, Energy Management Division of Facilities Management at The University of Alabama at Birmingham for proving technical information and for allowing access to the different buildings and for funding this project.

Sigma Xi – The Scientific Research Society for the Grants-in-Aid of Research for equipment purchase

Thank You!!!

Questions???