I would like to leave the readers with few questions:

I would like to leave the readers with few questions:

1) Who would be at a loss if the distribution lines are undergrounded & thus illegal tapping prevented?

2) Who would be at a profit if the losses reduce to a subcritical figure in the range 15-20%. ?

3) Who would benefit from consumer care centers?

4) Who would benefit from the continuous network monitoring &rapid fault correction?

5) And finally who would benefit from a 15+ hour power supply throughout the area ?

kindly post ur answers

Rights of Tribals Must be Protected: Shri DEO

Rights of Tribals Must be Protected: Shri DEO
Union Minister for Tribal Affairs. Shri V.Kishore Chandra Deo has called upon the states to cooperate with the centre in protecting the rights of the tribals. Addressing media persons in New Delhi today, the minister said, in no case the provisions of “The Scheduled Tribes and other Forest Dwellers Recognition of Forest Rights Act-2006” be violated and every government must be sincere and vigilant in its proper implementation. While taking up developmental initiatives like industry and mining, the traditional faiths, beliefs and lifestyles of tribals and other forest dwellers as well as environmental issues must not be ignored, the minster said.

Citing the recent ruling of Hon’ble Supreme Court, Shri Deo emphasized on holding GramSabhas in the affected villages and obtaining their approval before taking up any developmental projects.

Prime Minister’s address at ASSOCHAM Annual General Meeting

Prime Minister’s address at ASSOCHAM Annual General Meeting
The Prime Minister, Dr. Manmohan Singh addressed the 92nd Annual General Meeting of ASSOCHAM in New Delhi today. Following is the text of the Prime Minister’s address on the occasion:

“I am delighted to be with you today to inaugurate the ASSOCHAM’s AGM, 2013. ASSOCHAM has, over the years, provided valuable inputs from time to time for shaping our policies for economic and industrial growth. I would like to compliment Shri Rajkumar Dhoot and all his colleagues for their work and I am happy to share my thoughts with you today.

Let me begin by stating upfront that we, like most other countries, are going through a difficult period. I know that business is deeply concerned about the slowdown in our economy. It is looking to the government to bring the economy back to a higher growth path. This, I believe, is a legitimate expectation and is also upper most in our mind.

When things are going well, government should interfere as little as possible. When things are going bad, as they seem to be at present, it is the responsibility of the Government to become more pro-active.

The most immediate cause of worry is the recent volatility in foreign exchange markets. Much of this was due to global markets reacting to the likelihood of a withdrawal of Quantitative Easing III by the US Federal Reserve Bank. Large volumes of funds were withdrawn from emerging markets and there was a depreciation in many emerging market countries including Turkey, Brazil and South Africa.

We too experienced a significant depreciation in the exchange value of the rupee. In our case, it was perhaps exacerbated by the fact that our current account deficit in the balance of payment had increased to 4.7 percent of GDP in 2012-13.

I can assure you, we are committed to bringing the current account deficit under control by addressing both the demand side and the supply side of the problem. On the demand side, we need to reduce the demand for gold and the demand for petroleum products – the two biggest components of our trade deficit.

We have taken measures to control the demand for gold and I am happy to say they have had some effect. Gold imports declined sharply in June, and I hope they will stay at normal levels from now on.

On petroleum products, we began a process of correcting the prices of petroleum products last year. The gradual correction that was taking place in diesel prices had reduced the gap in under-recoveries from almost Rs 13 per litre to less than Rs 2 per litre. Unfortunately, some of this has been undone by the depreciation of the Rupee. However, our policy of adjusting prices to progressively eliminate under-recoveries remains in place.

On the supply side, we need to push our exports. The depreciation in the rupee will help. Of course, there is a time lag before this benefit will be felt in terms of export volumes, but orders being booked from now on would certainly benefit. We are also trying to remove the constraints in the export of iron and other ores which saw a considerable decline during the last one year.

The Reserve Bank has done its bit to stabilise market expectations. Initially it injected dollars into the market. This helped to some extent. More recently, it took additional steps to raise short term interest rates. These steps are not meant to signal an increase in the long term interest rates. They are designed to contain speculative pressure on the currency. Once these short term pressures have been contained, as I expect they will be, the Reserve Bank can even consider reversing these pressures.

Looking ahead, the rupee depreciation will help Indian industry to compete effectively with other countries, both in export markets and against their imports in our markets.

I hope industry is thinking seriously of how to become more competitive. It is because we are confident that it can that we have entered into Comprehensive Economic Partnership Agreement with the ASEAN countries as well as the Republic of Korea. We are hoping to conclude a similar agreement with the European Union soon.

Ideally we should bring the current account deficit down to 2.5 percent of our GDP. It is clearly not possible to do this in one year, but I expect that the current account deficit in 2013-14 will be much lower than the 4.7 percent level recorded last year. It will decline further next year. We will use all policy instruments available – fiscal, monetary and supply side interventions to ensure that the Current Account Deficit declines further over time.

Looking at the medium term prospects, I feel we can and we should remain optimistic. The basic fundamentals of our economy are sound and healthy. We have been taking all possible measures to correct imbalances on the macro front.

The fiscal deficit, which is the accumulated effect of the fiscal stimulus given in the past, had expanded and it needs to be reduced. The Finance Minister has targeted fiscal deficit of 4.8 percent of GDP in the year 2013-14 and announced continuing reductions of about half a percentage each year subsequently, up to 2016-17. We are determined to meet the target for this year.

We also need to take steps that will revive the momentum of investment. A major focus of concern in the past few months is that many projects have been held up for various reasons. We have seen a very strong expansion in power generation capacity but coal supply became a problem. We have now resolved this problem and the fuel supply agreements are being signed which will ensure that all plants that are commissioned by 2015 will have adequate supplies of coal consisting of a mix of domestic and imported coal.

Many projects have been held up for lack of regulatory approvals. These are being expedited. A separate cell has been set up in the Cabinet Secretariat recently to identify big ticket projects, both in the public and private sectors, and to see how they can be helped through various hurdles.

Infrastructure is absolutely critical for our medium term growth prospects and we are monitoring progress in this area on a quarterly basis. Several initiatives are being pursued.

• The Government has plans for setting up two major ports in Andhra Pradesh and in West Bengal.

• New airports are envisaged to come up in Navi Mumbai, Juhu, Goa, Pune and Kannur.

• At 50 other locations, new small airports are being built.

• Major railway projects, including an elevated rail corridor for Mumbai, are being processed.

• The feasibility of a bullet train from Mumbai to Ahmedabad is being studied.

• Industrial Corridors from Delhi to Mumbai, Amritsar to Kolkata and Chennai to Bangalore are being considered.

All these initiatives are being monitored at the highest level with a sense of urgency.

There are several other reforms that have been undertaken over the last one year.

• The Banking Laws have been amended to raise the cap on voting.

• Subsidy reform and rationalisation has started in full force. Direct Benefit Transfer Scheme is being rolled out across the country to reduce both wastage and corruption in delivery of public service.

• Foreign Direct Investment has been liberalised in single brand retail, multi-brand retail, civil aviation and power exchanges. More FDI reforms are on the anvil as has been reported.

• A new bank licensing policy has been announced and new licences are soon to be awarded.

• GAAR, which has been a subject matter of considerable concern to industry, has been postponed by 2 years and there is greater clarity on the rules.

• Taxation issues of the IT sector and of development centres have been resolved based on the Rangachary Committee report.

• Public Sector investment has been fast-tracked and I have estimated that over Rs 120,000 crores has been invested by major Public Sector Units last year.

• Infrastructure Debt Funds have been rolled out.

• Sugar has been fully decontrolled.

• Railways have corrected their fares for the first time in a decade.

• Construction has begun on the Dedicated Freight Corridor.

• The investment policy for urea has been approved.

• Gas pricing has been corrected to reflect market realities better.

• Procedural improvements have been made in the road sector to improve the economic viability of projects.

I could go on, but my purpose was only to show that we have acted on several fronts. We will persevere with these initiatives and I hope that their impact will be felt in the second half of this year.

I would not like to make a forecast of what our growth will be in the year 2013-14. The IMF has recently reduced its earlier projection of growth rates for all countries including India, for 2013. We had targeted 6.5 percent growth at the time the Budget was presented. But it looks as if it will be lower than that.

Industrial growth has not yet recovered. However, I am happy to say that agriculture looks well set to show a good performance. In fact, one of the important achievements of our Government is that agricultural performance has improved considerably. In the Tenth Plan period agriculture grew at 2.4 percent. In the Eleventh Plan period it grew at the rate of 3.6 percent. In the Twelfth Plan we have targeted 4 percent growth for our agricultural sector. I am hopeful that the current year, with the rains being plentiful thus far, agriculture will do well. This will help revive demand in rural areas which will contribute to stronger industrial performance in due course.

I must emphasise that it is not the exact growth number for 2013-14 that matters. What is important is that the economy should turn around from 5 percent achieved last year. There is a very good chance that we can achieve that with good agricultural performance and the effect of the various actions we are taking on infrastructure.

Thereafter we will try to accelerate to higher grounds in 2014-15.

Before concluding, let me address the issue of UPA Government’s performance. Our political critics focus on the experience of one bad year. This makes for good television but it is a very distorted picture. I invite you to consider the following.

• The average growth rate in the 8 years of the UPA from 2004-05 to 2012-13 was 8.2 percent per annum. This is much better than the 5.7 percent reached in the previous 8 years.

• I have already mentioned that agriculture did much better in the Eleventh Plan than in the Tenth Plan. This is reflected in real per capita rural consumption rising at 2.9 percent per year between 2004-05 and 2011-12 compared with only one percent increase between 1993-94 and 2004-05.

• Rural real wages have also risen much faster (6.8 percent per year in the 11th Plan as compared to an average of 1.1 percent per year in the ten years preceding it).

• The percentage of population below the poverty line declined at 0.75 percentage points per year before our government came to office in 2004-05. It has fallen more than 2 percentage points per year between 2004-05 and 2011-12.

I think this is a record that any government can be proud of. I agree we have had one bad year. I assure you we will get out of it.

I have touched upon some of the issues that I know concern the captains of industry and have talked about the areas where action needs to be taken. I assure you we will leave no stone unturned to ensure that our economy rebounds. I appeal to each one of you not to be overcome by negative sentiments. We should stay the course, and work together to achieve our collective national goals.

With these words, I wish this conference and the ASSOCHAM all success.”

Thank You.

STUDY, OPTIMIZE AND IMPLEMENT AUTOMATION IN CHILLER

A NEW DESIGN IN HOUSEHOLD CLOTHES TUMBLER DRYER

A NEW DESIGN IN HOUSEHOLD CLOTHES TUMBLER DRYER                                   

Abstract:

                This is a project done by us in R.N ENGINEERING in banglore guided by Mr.PRADEEP BANSAL(Design engineer.).This  paper explores the feasibility of a novel design of household clothes tumbler dryer, where the elec- trical elements of a standard tumbler clothes Dryer A (which heat the ambient air  entering the drum) were replaced by  a  water-to-air finned tube heat exchanger (Dryer B). To achieve the objective of  the study, experimental performances of the two dryers (e.g.,  Dryers A and B) were evaluated for  the same operating conditions. During the experiments, Dryer B was found to have shorter drying times, lower moisture extraction rates for  the same power input and hence significantly more efficient than Dryer A. This type of dryer may be adopted by the industry in the future for its relatively low  cost, higher energy efficiency and environmental benefits

Introduction :

Improved energy efficiency in both the domestic and commer- cial  environment is  an   engineering  challenge for  all  industries worldwide. All around the world, large scale Combined Heat and Power Plants (CHP) are  being built. These plants not  only  generate electricity but also  simultaneously produce process heat (in  terms of hot  water) that could be distributed to local  areas or large resi- dential apartments and buildings. The  overall efficiency of  these plants can  be  as  high as  90%, due to  the utilization of waste heat in  the form of hot  water from the plant. These power plants can be viable only  if process heat is required continuously throughout the year. To make the optimum use  of this hot  water supply, many household appliances can be adapted accordingly, such as a house- hold clothes tumbler dryer, where the heating element to heat the air in the dryer can be replaced with a water-to-air heat exchanger. Electricity is high grade and high quality energy that results in  a loss  of its  energy potential when used for  low  purpose work such as  heating applications. In  addition to  significant environmental benefits, hot  water would be  much cheaper than electricity.

This  paper evaluates the feasibility of a novel design of house- hold clothes tumbler dryer, where the electrical elements of a stan- dard tumbler clothes dryer (which heat the ambient air  entering the  drum)  were  replaced by   a  water-to-air finned tube  heat exchanger using hot  water as a medium. The performance compar- ison  of this unit with the identical conventional tumbler dryer has been  carried  out.   The   1.6 kW   electrical heater that  heats the

ambient air  entering the drum of  the standard Dryer A was   re- placed by a water-to-air, wavy finned tube heat exchanger (Dryer B).  Operating parameters  that  affect the  performance of   the adapted dryer such as mass flow  and temperature of water flowing through the heat exchanger were investigated.

2. Literature review – drying process and performance

A literature search on the topic suggests that the dryer put for- ward is new and has  not  been previously researched. However the performance and efficiency of traditional tumbler dryers have been investigated both experimentally and by computer models [1–8].

Lambert et al. [1] developed a model of the drying process with- in a domestic household dryer based on the laws of conservation of mass and energy. Characteristics of the drying process were exam- ined and these included the moisture content of the clothes and the rate of evaporation over  time. Bassily  and Colver  [2] examined the affect on drying times and energy consumption of a dryer when various operating  parameters  are   varied.  They   found  that  by increasing the drum load  (the weight of clothes), air flow  decreases and the area for mass transfer of water increases. These changes in- crease the rate of evaporation. Therefore, the energy consumption per  kg  of clothes decreases with increasing load.  The  increase  of heater power was  found to  increase the evaporation rate, hence decreasing drying time, while fan speed showed to have little influ- ence on  evaporation rate. Conde [3],  like  Lambert et al. [1]  devel- oped a simple model of the drying process, in which it was  found that lowering the partial pressure of  water in  the drying air  in- creases the speed of  the drying process. The  partial pressure  of water in  the drying air  can  be  lowered by  either decreasing the

:

Nomenclature

Cp                   specific heat of a fluid  (kJ kg—1  °C—1)

m             mass (kg)

m_              mass flow  rate (kg s—1)

MER        moisture extraction rate (kW h/kg)

t                time (s)

T             temperature (°C)

Q_               rate of heat transfer (kW)

Subscripts

in             inlet

out           outlet

w              associated with the  water

air  humidity content or increasing the temperature. High  temper- ature can  degrade the quality of clothes; therefore priority falls  on keeping the humidity content to a minimum. Deans [4] also  devel- oped a simple model of a dryer, from which it was  noted that the factors that influence the drying time are  the mass of clothes and the power input into the dryer. Bansal et al. [5] simulated the per- formance of conventional air  vented tumbler clothes dryers with two improved versions using heat recovery heat exchangers. They found that the open-cycle condensing dryer and the closed-cycle condensing dryer  with  heat  recovery were  significantly were respectively 14% and 7% more efficient than the air  vented dryer. Braun et al. [6]  found the performance of an  air  heat pump cycle for  tumbler clothes dryers was  up  to  40% more energy efficient than  the  conventional electric dryer as   against  14%  projected improvement by open-cycle and closed dryers using heat recovery heat exchangers.

Cooper [7]  analysed the performance of the Fisher and Paykel ED56  tumbler dryer and found that decreasing the power input of the dryer to 75% at latter stages of the drying cycle  increased en- ergy   consumption, however decreasing the power input to  50% showed marginal improvement. This  is because decreasing power input increased drying time and hence had little effect on the mois- ture extraction rate. An increase of air mass flow  was  found not  to increase energy efficiency. This is because the temperature that the air is entering the drum is lower, as the air is exposed to the heat- ing  elements for a shorter time.

Williamson and Bansal [8]  studied large commercial tumbler dryers in  which a model was  developed of a dryer incorporating heat recovery via an  air  to air  heat exchanger. This showed an  en- ergy  saving of 8%. However, having a  heat exchanger within the dryer system has  some disadvantages. Firstly, lint  may cause foul- ing of the heat exchanger, degrading its performance and secondly, a  pressure drop across the heat  exchanger increases fan  input power.

3. Description of the dryers

Experimentation  was   carried out   on   two  similar household tumbler dryers: a standard Dryer A (Fig. 1)  and a modified Dryer B model. For both machines, their dry  load  capacities were 4.5 kg and efficiency star ratings were 1 out  of 6. Both  also  incorporated reverse tumbling in which the drum and fan reverse their direction of  rotation. This  occurred every eight minutes for  Dryer A and every six  and a  half  minutes for  Dryer B. Dryer B was  modified by replacing its electrical heating element, located at the back,  with a heat exchanger as shown in Fig. 2.

3.1. Drying  process

3.1.1. Dryer  A

A schematic of the drying process for  the Dryer A is shown in Fig. 3. The inlet fan  draws ambient air  into the cabinet (1–2). This pressurises the cabinet (2–3) causing air  to  flow  over  the heating elements, which are  placed at the back  of the drum (3–4). Heated

Fig.  1.  Dryer A: conventional household tumbler dryer.

Fig.  2.  Back  of the modified Dryer B – with a heat exchanger installed.

air  then enters the drum and extracts moisture from wet clothes placed in  the drum (4–5). The  air  flows from the drum, through internal ducting, and is  then exhausted into the room through the rear of the cabinet (5–6).

3.1.2. Dryer  B

The  drying process of the modified Dryer B is the same as  for Dryer A except that ambient air  is heated by a heat exchanger be- tween 3 and 4 (see  Fig. 4), gaining heat from a hot  water supply.

3.2. Description of the  Heat  Exchanger

The  hot  water heat exchanger installed in  Dryer B consists of copper tubing and aluminium wavy fins,  as  shown in  Fig. 5. The hot  water passes through the tubes while air  flows over  the tubes and through the fins  perpendicular to  the direction of water flow. These extended fin  surfaces effectively improve the overall heat transfer performance of the heat exchanger [9].

4. Measure of performance

The  performance of a dryer can  be  characterised in  two main ways: moisture extraction rate (MER)  and the drying time [7,8].

Fig.  5.  Close up of the heat exchanger within the modified dryer.

dryer is better performing if it has  a lower MER and a shorter dry- ing  time.

MER is defined as the total power consumed multiplied by the dry- ing  time in  hours, divided by  the mass of water evaporated from the clothes (Eq.  (1)).  The  total power consumed by  Dryer A was that expended by the heating elements and the motor which drives

MER ¼

Q_  x t

mWater Removed

rkW h1

kg

ð1Þ

both the fan  and the drum. For  the modified Dryer B, the power consumed was  that expended by the electrical motor and the rate of heat supplied to  the air  from the water. Drying time is simply the time taken to  complete sufficient drying of  the clothes. The

5. Experimental approach

A matrix outlining the conducted experiments is shown in Table

1.  This  shows that two runs were performed on  Dryer A under

Fig.  3.  Drying process of Dryer A (a)  2D  schematic. (b)  3D  schematic – adapted from [4].

Fig.  4.  Drying process of the modified Dryer B.

Table 1

Details of experimental plan.

the power consumed by the heating elements from the power con- sumed by the dryer

Type of dryer

Drying variable               Test number

Test description

Q_ water-to-air ¼ m_ w Cp ðT w;in  — T w;out Þ                                                           ð3Þ

Dryer A     Control test                         1                   Performed under standard running conditions

2                   Performed under standard running conditions

Power to heaters    3                           Power input of 1.92 kW

4                   Power input of 1.59 kW

5                   Power input of 1.43 kW

For Dryer B, a power transducer was  used to measure the power drawn by  the electrical motor. The  rate of heat transfer from the water to  the air  in  the heat exchanger was   calculated from the measurements of temperatures taken from thermocouples on  the tubes of the heat exchanger and the mass flow  of water. The water mass flow  can  be  given by

Dryer B      Inlet water temperature

Water mass flow rate

6                   890 °C inlet water temp, water flow rate 0.1  kg/s

7                   880 °C inlet water temp, water flow rate 0.1  kg/s

8                   870 °C inlet water temp, water flow rate 0.1  kg/s

9                   880 °C inlet water temp, water flow rate 0.18 kg/s

10                 880 °C inlet water temp, water flow rate 0.07 kg/s

Q_ water-to-air ¼ m_ w Cp ðT w;in  — T w;out Þ                                                          ð3Þ

The  total power input for  the modified dryer is  therefore de- scribed by

Q_ total ¼ Q_ water-to-air þ ðQ_ fan  þ Q_ drum Þ                                                           ð4Þ

A Sartorius platform scale having a resolution of 5 g was  used to measure the mass of the clothes during a drying test cycle  without the removal of clothes from the drum. The pressure was  been mea- sured in two locations of the dryer: the drum and the cabinet. Two

normal running conditions (as  it  would run in  a household envi- ronment). The  test parameters included ambient air  temperature of  20–22 °C, inlet air  humidity of  55–65%  and a  power input of

1.73–1.75 kW.  These tests (1  and 2  in  Table  1)  were referred to as  the control tests and were repeated to  insure consistency in data. Following this, further tests were conducted with different power  inputs  whilst  keeping the  other  parameters  fixed. The MER and drying time values gained from the experiments on Dryer A formed the baseline data for comparison with Dryer B.

6. Experimental setup

6.1. Testing  method

The  two dryers were tested as  per   the AS/NZS 2442.1-1996 standard [10].  This  outlines how tests should be  carried out  on  a dryer to determine its performance. A standard 4.5 kg load  consist- ing of cotton of specific size and colour was  used for every test. The bone dry  mass of this load  is that of the material when it  has  no moisture. The  standard specifies that the test load  should weigh

190% of its  bone dry  mass value.

6.2. Sensors

Twelve thermocouples were employed in  Dryer A to  measure temperatures  at different locations, including inlet and exit   air, the heating element temperatures and the air  temperature at the back  of the drum. The  thermocouples were ‘radiation’ shielded to improve their accuracy. For  Dryer B, a  further 4  thermocouples were used to  measure the surface temperatures of  the tubes of the heat exchanger. These were used to  estimate the temperature of water flowing through the tubes. Thermo-paste was  placed be- tween the tube and thermocouples. The  thermocouples were se- cured with tape and wire and then insulated, ensuring no  air  gap between the couples and pipe and hence no  temperature gradient between them. The accuracy of the thermocouples was  found to be

±0.08  °C.

Two Humirel HM 1500LF humidity transducers, having an accu- racy  of 0.1% RH were employed to measure relative humidity (RH) at the inlet and outlet of the dryer. The  power input to  the dryers was  measured with two Carrel Precision transducers. One  to mea- sure the power input for the heating elements while the other was for the whole appliance. The consumption of power by the electri- cal motor that runs the drum and fan was  calculated by subtracting

pressure tappings were installed, one  at the drum door and the other at the rear of the cabinet. Air hoses connected these to  two manometers, with a  resolution of  ±10 Pa.  Air  volume flow   was measured using the ‘bag method’ [11].  This involved the construc- tion of a large plastic bag of known volume and minimal resistance. The  bag  was   then filled with exhaust air  over  a  measured time (Fig. 6), enabling the calculation of the volume flow.  Water, at con- stant temperature and flow,  was  supplied to the heat exchanger in Dryer B.

7. Experimental results and discussion

7.1. Analysis of the  drying  process  – Dryer  A

Variations in  load  mass and evaporation rate for  Dryer A over time is shown in Fig. 7. The  evaporation rate is zero at time zero, as  the clothes have just been put into the dryer. The  evaporation rate is also  zero at the end of the cycle,  since the dryer is turned off at this point. The drying process can  be divided into three suc- cessive phases: transient, constant and falling. The profiles of mass and evaporation rate were consistent between the two tests.

Corresponding exit  humidity and exit  temperatures are  shown in  Fig. 8.  In  the constant rate phase both relative humidity and temperature were 30 °C and 85% RH, respectively. In  the falling rate phase, air  temperature increases and relative humidity de- creases due to  reducing moisture in the clothes at this stage.

Fig.  6.  Plastic bag used to measure air flow rate.

Fig.  7.  Clothes mass (in  drum) and evaporation rate vs.  time in control tests for  Dryer A (see Table 1).

Fig.  8.  Relative humidity and temperature of exhaust air vs.  time in control tests for  Dryer A (see Table 1).

The  power input to  the heating elements and the total power input to  the dryer is  shown in  Fig.  9.  Power input is  constant throughout, except for vertical lines every 8 min when the drum’s rotation was  reversed.

7.2. Performance of Dryer  A with  different ratings

The MER and drying time for different power inputs for Dryer A are  shown in  Fig. 10.  As expected the drying time decreases with the increasing power input to the system. This is because the aver- age   temperatures entering the drum are   higher, increasing the driving force  for evaporation (Fig. 11). The exception to the general trends for  the drying time and MER was  the test with the total power input of 1.59  kW. The MER rate was  1.14  kW h/kg compared

to  the  average MER  of  the control tests of  1.17  kW h/kg.  This equates to  2.6% increase in efficiency.

7.3. Analysis of the  drying  process  – modified Dryer  B

Thermodynamic analysis of modified Dryer B is similar to Dryer A. Exhaust humidity, temperature, mass and evaporation rate over time are  the same for both dryers except the power input into the dryer here is due to hot  water, leading to different air temperature entering the drum.

7.3.1. Effect of heating water inlet  temperature

The  MER values and drying times for  tests done on  modified dryer, for a range of inlet water temperatures, are  given in Fig. 12.

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

Total Power

Heating Elements

0.0

0            20           40            60            80           100         120         140

Time (min)

Fig.  9.  Total power to dryer and power input to heating element vs.  time (see Eq. (2)).

Fig.  10.   MER and drying time for  different total power inputs for  Dryer A.

Fig.  11.   Average air temperature entering the drum with different power input vs.  time for  Dryer A.

Fig.  12.   MER and drying time for  different water inlet temperatures for  Dryer B.

Fig.  13.   Rate of heat transfer vs.  water inlet temperatures for  Dryer B.

Fig.  15.   Rate of heat transfer vs.  water mass flow rates for  Dryer B.

It is shown that increasing the inlet water temperature decreases the drying time. Increasing the water temperature from 66 °C to 86 °C yielded a decrease of drying time of 41 min (from 170  to 129  min). At an  inlet water temperature of 66 °C the clothes took 171  min

to  dry,  however the MER for  this test was  lower, 1.017 kW h/kg, compared to other tests. This was  3.7% more efficient compared to the MER from 79 °C inlet water temperature. This  test yielded the highest MER of 1.06  kW h/kg (as can  be seen in Fig. 13).

Fig.  14.   MER and drying time for  different water mass flow rates for  Dryer B.

Fig.  16.   MER and drying time for  different power inputs for  both the dryers.

7.3.2. Effect of mass  flow rate   of water

The MER values and drying times for tests with different flows are  given in  Fig. 14.  Water mass flow  does not  seem to  affect the drying time as  much as  changing the inlet water temperature. Increasing the mass flow   from 0.066 kg/s  to  0.18  kg/s  decreases the drying time by  7 min (from 145  to  138  min). This  is because changing the mass flow  of water does not  change the rate of heat transfer  appreciably (as   can   be   seen in  Fig.  15).   However the MER values are  within 1.3% of each other.

7.3.3.Other considerations

A close evaluation of  the HX surface after a  few  experiments indicates some signs of lint  formation, which may need attention before commercialization of the product.

7.4. Performance comparison of the  two  dryers

                         The MER values and the drying times for different power inputs for all tests are plotted in Fig. 14. The modified Dryer B dries the load 15–18 min quicker than Dryer A for the same power input, suggest- ing the modified dryer is more efficient. For the same power input, the modified dryer has MER approximately 0.1–0.12 kW h/kg lower than Dryer A- that is 75% lower MER. Indeed this modification of dryer, to use hot  water, is not  only  feasible but is also more efficient than the existing dryer with electrical elements. A literature search has shown that it is currently the only household appliance success- fully  running on hot  water.

Possible reasons for Dryer B being more efficient than Dryer A is that Dryer A suffers from loss of heat, where heating elements radi- ate  heat out  of the cabinet, which is then conducted through back plate and out  into the surroundings. It  is  probably less  than the heat radiated by  copper tubes containing hot  water. This  view is supported by the fact  that the temperatures entering the drum of Dryer B were higher for  same power input. Higher temperatures increase evaporation rate, decrease drying time and increase effi- ciency (as  can  be  seen in Fig. 16).

Another reason why the modified dryer is more efficient is be- cause its  air  mass flow  is slightly higher: 0.032 kg/s  compared to

0.030 kg/s.  This means that the air residence time within the drum is lower resulting in higher driving potential for  evaporation. This is however contradictory to  the findings of Cooper [7]  who found that increasing flow  rate by  5% would have little effect on  dryer efficiency.

8. Conclusions

In this study, a new design of a household clothes tumbler dryer was  successfully modified by replacing its electrical elements with a heat exchanger to  utilise hot  water to  dry  clothes. The  modified Dryer B for  the same total power input had drying times 15–

18 min shorter MER value (i.e.,  0.1–0.12kW h/kg lower) meaning that it is significantly more efficient (i.e., about 11%) than the con- ventional dryer. Increasing the inlet water temperature to the heat exchanger of the modified Dryer B decreased the drying time sig- nificantly but increased the MER value and hence less  efficient.

Decreasing the power input into the heaters of  Dryer A, in- creases the drying time as  the temperatures entering the drum are  lower, leading to  only  subtle effects on  the MER value as  any decrease in power input is usually offset by the increase in drying time. However the drying run on Dryer A with total power input of

1.59  kW is 2.6% more efficient than the dryer under standard oper- ating conditions (average of 1.74  kW  total power). A power input of a lower of higher value than 1.59  kW  into the dryer yielded a slightly higher MER value. It is recommended that further research and development should be undertaken to assess if lint  fouling on the fins  of  the heat exchanger may have any  long  term perfor- mance issues.

Referens

[1]   A.J.D. Lambert, F.P.M.  Spruit, J. Claus, Modelling as a tool for  evaluating the effects of energy-saving measures. Case study: a tumbler drier, Applied Energy

38 (1991) 33–47.

[2]   A.M.  Bassily, G.M.  Colver, Performance  analysis  of  an electric clothes dryer, Drying Technology 21 (3)  (2003) 500–524.

[3]   M.R.  Conde, Energy conservation with tumbler  drying in laundries, Applied

Thermal Engineering 17 (12) (1997) 1163–1172.

  [4]     N.  Williamson,  P.K.  Bansal,  An   experimental  investigation on  the  energy                efficiency of  gas commercial laundry dryers

Engineering 218 (2004) 143–152.